<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:2f052cf7-e810-479d-ab53-11645c61aa9a,g:69c1d108-24c8-482c-a826-3a2e78a58f25-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://fluenceenergy.com/role/Cover" xlink:type="simple" xlink:href="flnc-20221231.xsd#Cover"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/Cover" xlink:type="extended" id="i7a8b24e2b47746f5b90ee89e81b3dcaa_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_20876dbf-150d-408c-9464-d78bea3b68d1" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentType_20876dbf-150d-408c-9464-d78bea3b68d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_2ad6625f-e82a-49bc-8abf-78c81cbad9dd" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentQuarterlyReport_2ad6625f-e82a-49bc-8abf-78c81cbad9dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_95ed0555-cdcc-4d68-b5e8-c6b9a45c544e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentPeriodEndDate_95ed0555-cdcc-4d68-b5e8-c6b9a45c544e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_3accfa15-c5c4-40e0-9bff-d7c382667e6b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentTransitionReport_3accfa15-c5c4-40e0-9bff-d7c382667e6b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_0d07307d-0f84-4b85-bfe1-4cfdd3b63bb5" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityFileNumber_0d07307d-0f84-4b85-bfe1-4cfdd3b63bb5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_ebeb609f-8a4c-4057-9eac-fbf5fdd5f9fa" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityRegistrantName_ebeb609f-8a4c-4057-9eac-fbf5fdd5f9fa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_cb09e2cd-7760-42a6-b346-dc57f595015a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityIncorporationStateCountryCode_cb09e2cd-7760-42a6-b346-dc57f595015a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_05e551c3-d9ea-4b85-82d7-d5e353bbb3e0" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityTaxIdentificationNumber_05e551c3-d9ea-4b85-82d7-d5e353bbb3e0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_dfbe6b46-32c4-4bce-8a8f-c0b94dd52d97" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityAddressAddressLine1_dfbe6b46-32c4-4bce-8a8f-c0b94dd52d97" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_9bb1469a-95c5-4ac9-a875-994af06de635" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityAddressAddressLine2_9bb1469a-95c5-4ac9-a875-994af06de635" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_3bc06359-d6db-4330-9794-bf89a463d65d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityAddressCityOrTown_3bc06359-d6db-4330-9794-bf89a463d65d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_f5c884ff-3539-4d72-9377-7f6e298e7584" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityAddressStateOrProvince_f5c884ff-3539-4d72-9377-7f6e298e7584" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_104af421-b050-4ed4-8383-f74a109d1bed" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityAddressPostalZipCode_104af421-b050-4ed4-8383-f74a109d1bed" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_3cbbc2db-e778-4705-8dc8-35e607668921" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_CityAreaCode_3cbbc2db-e778-4705-8dc8-35e607668921" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_167b8571-229e-44f2-8f77-808611e50f58" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_LocalPhoneNumber_167b8571-229e-44f2-8f77-808611e50f58" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_337353bf-c576-4b6e-bf20-ee81147f2013" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_Security12bTitle_337353bf-c576-4b6e-bf20-ee81147f2013" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_35c72582-c691-4854-9724-6ed428c1b14a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_TradingSymbol_35c72582-c691-4854-9724-6ed428c1b14a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_9fd397c8-4c1a-4177-a7f9-670c40f9d577" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_SecurityExchangeName_9fd397c8-4c1a-4177-a7f9-670c40f9d577" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_f8c96c0c-6fdf-44db-8227-b94a641ba6b9" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityCurrentReportingStatus_f8c96c0c-6fdf-44db-8227-b94a641ba6b9" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_30035b22-b6f8-4f7c-a821-a75d2a7af543" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityInteractiveDataCurrent_30035b22-b6f8-4f7c-a821-a75d2a7af543" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_0d83b14f-dc66-4bf8-828c-845052f3533e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityFilerCategory_0d83b14f-dc66-4bf8-828c-845052f3533e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_c4160846-2395-4c17-ac09-a627f2c9e866" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntitySmallBusiness_c4160846-2395-4c17-ac09-a627f2c9e866" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_1587e066-b44c-4010-8c06-857bc103fbb3" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityEmergingGrowthCompany_1587e066-b44c-4010-8c06-857bc103fbb3" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_7bef19ed-f34a-4d90-994f-a5d282962425" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityExTransitionPeriod_7bef19ed-f34a-4d90-994f-a5d282962425" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_22d66fbf-54bb-4b28-a030-76aa43ea0b63" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityShellCompany_22d66fbf-54bb-4b28-a030-76aa43ea0b63" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_b1f3700f-1bd7-4624-b600-0e173d425fe8" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_b1f3700f-1bd7-4624-b600-0e173d425fe8" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_8194a57c-5638-4c65-8902-b40984f6077a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_EntityCentralIndexKey_8194a57c-5638-4c65-8902-b40984f6077a" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_0527ada3-bb6d-4699-8601-ea5edacde595" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_CurrentFiscalYearEndDate_0527ada3-bb6d-4699-8601-ea5edacde595" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_9cc2ab0f-edfa-4675-bb5d-00b3aae22604" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentFiscalYearFocus_9cc2ab0f-edfa-4675-bb5d-00b3aae22604" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_1a8277b1-b240-4866-a2b2-f64b036b4034" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_DocumentFiscalPeriodFocus_1a8277b1-b240-4866-a2b2-f64b036b4034" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_bad0ab0e-76e4-4398-aac2-ef8e4626fb1c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_dei_AmendmentFlag_bad0ab0e-76e4-4398-aac2-ef8e4626fb1c" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_38203b28-800e-475c-b69c-761fd7a26190" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_0932d854-f0b7-4f9e-b0fe-16b6202fffad" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_38203b28-800e-475c-b69c-761fd7a26190" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_d48e3c20-a453-4116-afcd-d28368c46fbb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_38203b28-800e-475c-b69c-761fd7a26190" xlink:to="loc_us-gaap_StatementClassOfStockAxis_d48e3c20-a453-4116-afcd-d28368c46fbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d48e3c20-a453-4116-afcd-d28368c46fbb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d48e3c20-a453-4116-afcd-d28368c46fbb" xlink:to="loc_us-gaap_ClassOfStockDomain_d48e3c20-a453-4116-afcd-d28368c46fbb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_955dcc49-429e-49e3-acb2-fbf18b4f732c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d48e3c20-a453-4116-afcd-d28368c46fbb" xlink:to="loc_us-gaap_ClassOfStockDomain_955dcc49-429e-49e3-acb2-fbf18b4f732c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_90652408-786a-4b98-beff-b2e43a1df9b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_955dcc49-429e-49e3-acb2-fbf18b4f732c" xlink:to="loc_us-gaap_CommonClassAMember_90652408-786a-4b98-beff-b2e43a1df9b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB1Member_418cb2de-f765-4718-a192-bf62612aff16" xlink:href="flnc-20221231.xsd#flnc_CommonClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_955dcc49-429e-49e3-acb2-fbf18b4f732c" xlink:to="loc_flnc_CommonClassB1Member_418cb2de-f765-4718-a192-bf62612aff16" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="flnc-20221231.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i5061a240a1a04a279aacc659b82b0a22_CONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_97c2943d-0c21-4c9c-bb2f-4339ec61feba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_baa508ac-d52c-4dcc-bd0b-21a8d59ff5b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_97c2943d-0c21-4c9c-bb2f-4339ec61feba" xlink:to="loc_us-gaap_AssetsAbstract_baa508ac-d52c-4dcc-bd0b-21a8d59ff5b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_baa508ac-d52c-4dcc-bd0b-21a8d59ff5b2" xlink:to="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_dc76c70a-2ab2-4cf1-810b-528b69ff05e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_dc76c70a-2ab2-4cf1-810b-528b69ff05e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_c0d6b349-26e1-4195-ab15-bd4929019f4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_RestrictedCashCurrent_c0d6b349-26e1-4195-ab15-bd4929019f4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_75524dc3-6579-4518-b9fa-dfccd873ed2b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_ShortTermInvestments_75524dc3-6579-4518-b9fa-dfccd873ed2b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_4368a70c-64c6-4268-97b0-3cfdf64ff911" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_4368a70c-64c6-4268-97b0-3cfdf64ff911" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_823aff58-f19a-46f3-9ea9-08f6b8f44c48" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_823aff58-f19a-46f3-9ea9-08f6b8f44c48" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueFromRelatedPartiesCurrent_32c1bb82-d7db-42a1-97f4-04668dcf1520" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DueFromRelatedPartiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_DueFromRelatedPartiesCurrent_32c1bb82-d7db-42a1-97f4-04668dcf1520" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvancesOnInventoryPurchases_77f8f310-bb0a-455d-b815-deb9c5a63827" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdvancesOnInventoryPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_AdvancesOnInventoryPurchases_77f8f310-bb0a-455d-b815-deb9c5a63827" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_597bf57c-ddf8-4979-b46b-a79ba6546b99" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_InventoryNet_597bf57c-ddf8-4979-b46b-a79ba6546b99" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_d4020905-c0d6-4c03-803d-0599731c15e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_OtherAssetsCurrent_d4020905-c0d6-4c03-803d-0599731c15e7" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_7e63e715-70c9-48b8-a32a-b07eca5cb856" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_67ca6c2d-ca40-4ef7-b6e0-8e8267accaea" xlink:to="loc_us-gaap_AssetsCurrent_7e63e715-70c9-48b8-a32a-b07eca5cb856" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_baa508ac-d52c-4dcc-bd0b-21a8d59ff5b2" xlink:to="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3a8b21ba-a4b1-431c-b155-4946c83e6f39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3a8b21ba-a4b1-431c-b155-4946c83e6f39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_ac69945d-6942-4adf-941a-0790d07bde4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_ac69945d-6942-4adf-941a-0790d07bde4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ceb7f259-19f9-48a9-8485-f5c8401fe9cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ceb7f259-19f9-48a9-8485-f5c8401fe9cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_5a0b1aa8-b330-419d-954e-405b777e71af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_Goodwill_5a0b1aa8-b330-419d-954e-405b777e71af" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_d7f286d2-97ae-45c0-911b-d83ded053ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_d7f286d2-97ae-45c0-911b-d83ded053ba4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_AdvancesOnInventoryPurchasesNoncurrent_e7c215d1-161c-4cd3-9331-aaa92eaaf475" xlink:href="flnc-20221231.xsd#flnc_AdvancesOnInventoryPurchasesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_flnc_AdvancesOnInventoryPurchasesNoncurrent_e7c215d1-161c-4cd3-9331-aaa92eaaf475" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_9295a43e-694a-4967-89aa-d4ae9b71940b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_9295a43e-694a-4967-89aa-d4ae9b71940b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesAndLoansReceivableNetNoncurrent_bac2f4fa-7948-49a6-9ec5-30912bff75da" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesAndLoansReceivableNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_NotesAndLoansReceivableNetNoncurrent_bac2f4fa-7948-49a6-9ec5-30912bff75da" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_3911fd43-6691-40c4-b6f9-6366c1536089" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_3911fd43-6691-40c4-b6f9-6366c1536089" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrent_aa98f9ab-8599-4746-9cf8-b70147c52829" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_22d31fa5-4a4f-4b8f-9809-6b50cd17b002" xlink:to="loc_us-gaap_AssetsNoncurrent_aa98f9ab-8599-4746-9cf8-b70147c52829" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_b8ca530c-9a40-4428-b95a-99a2055317ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_baa508ac-d52c-4dcc-bd0b-21a8d59ff5b2" xlink:to="loc_us-gaap_Assets_b8ca530c-9a40-4428-b95a-99a2055317ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_97c2943d-0c21-4c9c-bb2f-4339ec61feba" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_d65a7c48-cab0-4188-a1cb-4c563cb9b421" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_AccountsPayableCurrent_d65a7c48-cab0-4188-a1cb-4c563cb9b421" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ContractWithCustomerLiabilityConsolidatedEntitiesExcludingAffiliatedEntitiesCurrent_8067887d-7eb7-4e3d-8bcb-38bdb407c142" xlink:href="flnc-20221231.xsd#flnc_ContractWithCustomerLiabilityConsolidatedEntitiesExcludingAffiliatedEntitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_flnc_ContractWithCustomerLiabilityConsolidatedEntitiesExcludingAffiliatedEntitiesCurrent_8067887d-7eb7-4e3d-8bcb-38bdb407c142" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_5e9d60d4-a35b-4d05-a50b-f580d710c31c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_5e9d60d4-a35b-4d05-a50b-f580d710c31c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_84541a08-82e2-4b5a-b403-32ad5d676a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_84541a08-82e2-4b5a-b403-32ad5d676a5c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_DueToRelatedPartiesAndContractWithCustomerAffiliatedEntitiesLiabilityCurrent_e944ecc0-fa12-4fe1-8d79-5a64de1095b3" xlink:href="flnc-20221231.xsd#flnc_DueToRelatedPartiesAndContractWithCustomerAffiliatedEntitiesLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_flnc_DueToRelatedPartiesAndContractWithCustomerAffiliatedEntitiesLiabilityCurrent_e944ecc0-fa12-4fe1-8d79-5a64de1095b3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxesPayableCurrent_d47f1817-e5a7-4e83-ac8b-ef5c4e43dd34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TaxesPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_TaxesPayableCurrent_d47f1817-e5a7-4e83-ac8b-ef5c4e43dd34" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_d79dda23-abbf-40bf-8b86-300c8fb38fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_d79dda23-abbf-40bf-8b86-300c8fb38fe9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_cfd5ee6f-c20a-46e6-b30e-e96aa904c7d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_cfd5ee6f-c20a-46e6-b30e-e96aa904c7d2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_4997dd7a-68dd-4897-8d28-dfa2959ca691" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_76b50ce2-9e53-4887-b5eb-bf8bc61c4d4f" xlink:to="loc_us-gaap_LiabilitiesCurrent_4997dd7a-68dd-4897-8d28-dfa2959ca691" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:to="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_3987423b-1ce5-4bed-9534-f48110e93d94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_3987423b-1ce5-4bed-9534-f48110e93d94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_8e2222af-03a9-42c8-b4f5-d30ad428d0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_8e2222af-03a9-42c8-b4f5-d30ad428d0c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_f8ade8ba-d30c-4949-ac54-329dd3e6180b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_f8ade8ba-d30c-4949-ac54-329dd3e6180b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_c2d3b365-b3a1-4435-aca3-291cd663c111" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_c2d3b365-b3a1-4435-aca3-291cd663c111" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_da19a9ce-8499-4740-a26c-41b435266c12" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_bcd18a1a-a2c9-4906-b1bf-8ffe2c209a5b" xlink:to="loc_us-gaap_LiabilitiesNoncurrent_da19a9ce-8499-4740-a26c-41b435266c12" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_618f3e96-1610-4855-bb24-edcfa1c4b466" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:to="loc_us-gaap_Liabilities_618f3e96-1610-4855-bb24-edcfa1c4b466" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:to="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_1ef42c4d-1239-439e-9c97-e9ea88d2c654" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_PreferredStockValue_1ef42c4d-1239-439e-9c97-e9ea88d2c654" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_1db0bd86-b4d4-4c37-a40e-c9adce7eb553" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_CommonStockValue_1db0bd86-b4d4-4c37-a40e-c9adce7eb553" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_c61e069b-380f-4aa3-a7fb-e39ff0123726" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_TreasuryStockValue_c61e069b-380f-4aa3-a7fb-e39ff0123726" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_a241336c-900d-45aa-ba64-31ddca70068e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_AdditionalPaidInCapital_a241336c-900d-45aa-ba64-31ddca70068e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8af67764-40fc-4123-98c6-468754a1e00a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8af67764-40fc-4123-98c6-468754a1e00a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8a955834-9456-4c2f-a6de-784c8c5e868a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8a955834-9456-4c2f-a6de-784c8c5e868a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_354f4eae-45cd-4be9-8c9b-b9e2f99e1da6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_StockholdersEquity_354f4eae-45cd-4be9-8c9b-b9e2f99e1da6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_dee0f878-b88c-4e4c-9b59-0bfe05def5cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_MinorityInterest_dee0f878-b88c-4e4c-9b59-0bfe05def5cc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_55592108-0ccb-40cf-bebb-ade138df2094" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_8eb43440-af5f-483a-a300-023300dba6dc" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_55592108-0ccb-40cf-bebb-ade138df2094" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_4dbee68d-13e7-473b-a008-6290c3274daf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b88b86ad-ea85-41e7-ac70-f13ccd71de06" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_4dbee68d-13e7-473b-a008-6290c3274daf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_86a61f40-e99b-43a7-a7cd-3186aba4e454" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_97c2943d-0c21-4c9c-bb2f-4339ec61feba" xlink:to="loc_us-gaap_StatementTable_86a61f40-e99b-43a7-a7cd-3186aba4e454" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3520f195-b36d-4ce0-ac80-e39543e61bef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_86a61f40-e99b-43a7-a7cd-3186aba4e454" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3520f195-b36d-4ce0-ac80-e39543e61bef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_3520f195-b36d-4ce0-ac80-e39543e61bef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3520f195-b36d-4ce0-ac80-e39543e61bef" xlink:to="loc_us-gaap_ClassOfStockDomain_3520f195-b36d-4ce0-ac80-e39543e61bef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_2c937fd1-68be-4ba0-b617-df2b6fe696b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3520f195-b36d-4ce0-ac80-e39543e61bef" xlink:to="loc_us-gaap_ClassOfStockDomain_2c937fd1-68be-4ba0-b617-df2b6fe696b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_07acade7-455d-4359-9e8e-1f5571f31acb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2c937fd1-68be-4ba0-b617-df2b6fe696b7" xlink:to="loc_us-gaap_CommonClassAMember_07acade7-455d-4359-9e8e-1f5571f31acb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB1Member_22f94231-6ed6-48fb-b0ed-cc5861986586" xlink:href="flnc-20221231.xsd#flnc_CommonClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2c937fd1-68be-4ba0-b617-df2b6fe696b7" xlink:to="loc_flnc_CommonClassB1Member_22f94231-6ed6-48fb-b0ed-cc5861986586" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB2Member_f8027a9f-e1e6-49f6-ad2c-34638f423961" xlink:href="flnc-20221231.xsd#flnc_CommonClassB2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2c937fd1-68be-4ba0-b617-df2b6fe696b7" xlink:to="loc_flnc_CommonClassB2Member_f8027a9f-e1e6-49f6-ad2c-34638f423961" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSPARENTHETICAL" xlink:type="simple" xlink:href="flnc-20221231.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSPARENTHETICAL"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSPARENTHETICAL" xlink:type="extended" id="i77f798e9320b40198289ade1857984bd_CONDENSEDCONSOLIDATEDBALANCESHEETSPARENTHETICAL">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_5dcd6a67-8f14-4366-a58d-de849c35158e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_5dcd6a67-8f14-4366-a58d-de849c35158e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_7f549b8e-26a2-440d-aacd-fc2911f16dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_7f549b8e-26a2-440d-aacd-fc2911f16dd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_f7e31deb-7841-40e9-aa7d-a94e158ceff6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_PreferredStockSharesIssued_f7e31deb-7841-40e9-aa7d-a94e158ceff6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_cce264e6-2a1e-4a55-9518-6cd4c29fdcc1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_cce264e6-2a1e-4a55-9518-6cd4c29fdcc1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_a3c9a54b-0de3-4024-b73d-717fd60f1a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_a3c9a54b-0de3-4024-b73d-717fd60f1a7a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_2a793440-ae33-4372-9b47-aa9114df8055" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_2a793440-ae33-4372-9b47-aa9114df8055" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_68ddfbf5-117c-4998-b0db-c3d81284416b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_CommonStockSharesIssued_68ddfbf5-117c-4998-b0db-c3d81284416b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_90b0b8bb-528a-4972-a90f-b3f9e95b146d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_90b0b8bb-528a-4972-a90f-b3f9e95b146d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_9b0f38ca-f2d1-4bd9-94df-3641584a3e27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1a92ab09-7058-468b-8fdf-881768b9582b" xlink:to="loc_us-gaap_StatementTable_9b0f38ca-f2d1-4bd9-94df-3641584a3e27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f0566f06-97f7-4823-af7e-6ded89d250e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9b0f38ca-f2d1-4bd9-94df-3641584a3e27" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f0566f06-97f7-4823-af7e-6ded89d250e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f0566f06-97f7-4823-af7e-6ded89d250e2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f0566f06-97f7-4823-af7e-6ded89d250e2" xlink:to="loc_us-gaap_ClassOfStockDomain_f0566f06-97f7-4823-af7e-6ded89d250e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9a114bf4-f562-4646-b580-4b3c29b23e3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f0566f06-97f7-4823-af7e-6ded89d250e2" xlink:to="loc_us-gaap_ClassOfStockDomain_9a114bf4-f562-4646-b580-4b3c29b23e3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_99433ab7-6b59-4282-b86c-82ca915e3389" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9a114bf4-f562-4646-b580-4b3c29b23e3c" xlink:to="loc_us-gaap_CommonClassAMember_99433ab7-6b59-4282-b86c-82ca915e3389" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB1Member_a1d9f611-0ad9-4412-9efe-21582124ba7c" xlink:href="flnc-20221231.xsd#flnc_CommonClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9a114bf4-f562-4646-b580-4b3c29b23e3c" xlink:to="loc_flnc_CommonClassB1Member_a1d9f611-0ad9-4412-9efe-21582124ba7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB2Member_cd11aeef-3e86-4387-9682-de20e22a74bc" xlink:href="flnc-20221231.xsd#flnc_CommonClassB2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9a114bf4-f562-4646-b580-4b3c29b23e3c" xlink:to="loc_flnc_CommonClassB2Member_cd11aeef-3e86-4387-9682-de20e22a74bc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVELOSSUNAUDITED" xlink:type="simple" xlink:href="flnc-20221231.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVELOSSUNAUDITED"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVELOSSUNAUDITED" xlink:type="extended" id="i3e470237a3ca4324b7454f4c711350a9_CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVELOSSUNAUDITED">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_835a475a-4547-4922-bfc5-947612d357fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_835a475a-4547-4922-bfc5-947612d357fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_e9bb9fc1-feff-4e80-b7c5-8963ef597b59" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_e9bb9fc1-feff-4e80-b7c5-8963ef597b59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_3a30b186-36dd-4326-b1d9-b5c19c5235f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_GrossProfit_3a30b186-36dd-4326-b1d9-b5c19c5235f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_738e5f4d-91e7-488b-aebb-58f581487598" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_738e5f4d-91e7-488b-aebb-58f581487598" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_db523797-48b2-4a0d-abd8-e4f55684985a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_SellingAndMarketingExpense_db523797-48b2-4a0d-abd8-e4f55684985a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_502ddd7b-ca6e-4f6a-bb7d-0fdb6eb01779" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_502ddd7b-ca6e-4f6a-bb7d-0fdb6eb01779" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_9c802d11-57c1-48c4-8261-bf738f76130d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_DepreciationAndAmortization_9c802d11-57c1-48c4-8261-bf738f76130d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_d75c49f0-5a6f-4d58-b604-09227cc48fbc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_InterestExpense_d75c49f0-5a6f-4d58-b604-09227cc48fbc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_8b2f7e6b-1e65-4760-ba78-7dfeb1ca3193" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_a4a1a0b2-5948-4cc3-88b6-4fa9a9ef7de2" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_8b2f7e6b-1e65-4760-ba78-7dfeb1ca3193" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_02fa22e4-28d8-40ed-ab43-f9b4f466f892" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_02fa22e4-28d8-40ed-ab43-f9b4f466f892" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_74849417-be16-436b-8371-dfc8aa6a2fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_74849417-be16-436b-8371-dfc8aa6a2fb4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_bbdeda33-4f8c-4602-ac56-c7be89fa3e2a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_ProfitLoss_bbdeda33-4f8c-4602-ac56-c7be89fa3e2a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_421ccd71-e5bf-414f-a9ff-25e17a91b5b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_421ccd71-e5bf-414f-a9ff-25e17a91b5b5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_bb07c107-5358-4355-91f6-4a642b251af7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_NetIncomeLoss_bb07c107-5358-4355-91f6-4a642b251af7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_80210d87-d20e-48f2-9cde-d4146a1d9152" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_80210d87-d20e-48f2-9cde-d4146a1d9152" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_37a6010c-d6e4-40dc-8fd4-83403f9c1f69" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_80210d87-d20e-48f2-9cde-d4146a1d9152" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_37a6010c-d6e4-40dc-8fd4-83403f9c1f69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1b0a0fd7-8176-4ff0-b261-1db1ba1fa630" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_80210d87-d20e-48f2-9cde-d4146a1d9152" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1b0a0fd7-8176-4ff0-b261-1db1ba1fa630" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_12425542-b1d1-4756-bcd3-d812d253eca1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_EarningsPerShareAbstract_12425542-b1d1-4756-bcd3-d812d253eca1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_aa4d877c-634b-41f8-a5d9-e864539e8638" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_12425542-b1d1-4756-bcd3-d812d253eca1" xlink:to="loc_us-gaap_EarningsPerShareBasic_aa4d877c-634b-41f8-a5d9-e864539e8638" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_9eb0fdd1-c1e7-49c9-aab2-984db277a82d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_12425542-b1d1-4756-bcd3-d812d253eca1" xlink:to="loc_us-gaap_EarningsPerShareDiluted_9eb0fdd1-c1e7-49c9-aab2-984db277a82d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_ef86d40e-76e6-4963-9e00-cfdf78c99c8b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_ef86d40e-76e6-4963-9e00-cfdf78c99c8b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_7f05441c-48c7-4b4a-a17d-4e4bbbb842df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_7f05441c-48c7-4b4a-a17d-4e4bbbb842df" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_c5c5c585-f1c5-4b6c-87b6-7799d663cf0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_c5c5c585-f1c5-4b6c-87b6-7799d663cf0c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_3b934adf-adf7-4042-90b4-71933a3e790d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_3b934adf-adf7-4042-90b4-71933a3e790d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_cb2f5e33-0279-4c61-be7c-912728af6161" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_cb2f5e33-0279-4c61-be7c-912728af6161" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_d68b6442-7a52-4ed6-92d2-79d3df45f142" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0f2b5a4b-dc3d-4d3f-93b0-95291d0c4a1e" xlink:to="loc_us-gaap_StatementTable_d68b6442-7a52-4ed6-92d2-79d3df45f142" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_7fef8aad-c0b5-499a-9364-a11729cf16dc" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d68b6442-7a52-4ed6-92d2-79d3df45f142" xlink:to="loc_srt_ConsolidatedEntitiesAxis_7fef8aad-c0b5-499a-9364-a11729cf16dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_7fef8aad-c0b5-499a-9364-a11729cf16dc_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7fef8aad-c0b5-499a-9364-a11729cf16dc" xlink:to="loc_srt_ConsolidatedEntitiesDomain_7fef8aad-c0b5-499a-9364-a11729cf16dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e0bb27e5-3d1e-44c9-bb2a-b01fb43b53eb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7fef8aad-c0b5-499a-9364-a11729cf16dc" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e0bb27e5-3d1e-44c9-bb2a-b01fb43b53eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember_457c67b1-be0b-4ec3-8bb8-33c240881e3f" xlink:href="flnc-20221231.xsd#flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e0bb27e5-3d1e-44c9-bb2a-b01fb43b53eb" xlink:to="loc_flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember_457c67b1-be0b-4ec3-8bb8-33c240881e3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_23838bcf-c333-4855-926f-a9a54b85d126" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e0bb27e5-3d1e-44c9-bb2a-b01fb43b53eb" xlink:to="loc_srt_AffiliatedEntityMember_23838bcf-c333-4855-926f-a9a54b85d126" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYMEMBERSEQUITYDEFICITANDMEZZANINEEQUITYUNAUDITED" xlink:type="simple" xlink:href="flnc-20221231.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYMEMBERSEQUITYDEFICITANDMEZZANINEEQUITYUNAUDITED"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYMEMBERSEQUITYDEFICITANDMEZZANINEEQUITYUNAUDITED" xlink:type="extended" id="i8af304964d654a25a5ec8371d498b4b3_CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYMEMBERSEQUITYDEFICITANDMEZZANINEEQUITYUNAUDITED">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4a6f3170-fa66-4e29-9cbb-f41fc360d0bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_c3a14043-98d6-42dd-bcfd-16779f168b18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4a6f3170-fa66-4e29-9cbb-f41fc360d0bc" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_c3a14043-98d6-42dd-bcfd-16779f168b18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_d8876eab-b9aa-401c-8c42-8f38ac99b098" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_c3a14043-98d6-42dd-bcfd-16779f168b18" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_d8876eab-b9aa-401c-8c42-8f38ac99b098" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_TemporaryEquityValueConversionOfConvertibleSecurities_718561de-9da6-4a7b-9c57-4649b98154f0" xlink:href="flnc-20221231.xsd#flnc_TemporaryEquityValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_c3a14043-98d6-42dd-bcfd-16779f168b18" xlink:to="loc_flnc_TemporaryEquityValueConversionOfConvertibleSecurities_718561de-9da6-4a7b-9c57-4649b98154f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_c3f7c659-0ceb-42a0-a7ef-9f1a5d26812a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4a6f3170-fa66-4e29-9cbb-f41fc360d0bc" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_2c28e69b-ed36-4c5c-9cb7-bd108e559a45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_2c28e69b-ed36-4c5c-9cb7-bd108e559a45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_833c396c-48d1-4852-86c6-884a81aa90a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_TreasuryStockCommonShares_833c396c-48d1-4852-86c6-884a81aa90a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e8aae415-ec36-48fb-83ca-4f426213edb0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e8aae415-ec36-48fb-83ca-4f426213edb0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MembersEquity_dbe515de-ffcb-4fd8-83b8-74d5cedcad4c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MembersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_MembersEquity_dbe515de-ffcb-4fd8-83b8-74d5cedcad4c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_e83c1354-a968-4eb9-9046-2c7e0e45c9d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_ProfitLoss_e83c1354-a968-4eb9-9046-2c7e0e45c9d1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_faeb4b8c-5803-4134-8401-b95b3e8d6186" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_faeb4b8c-5803-4134-8401-b95b3e8d6186" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c7e2ae3e-1808-4e7f-9745-4f1f601c79b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c7e2ae3e-1808-4e7f-9745-4f1f601c79b8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_3fa96c81-77f4-41e8-990e-a059952bcf20" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_3fa96c81-77f4-41e8-990e-a059952bcf20" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_ba79696d-830b-44fc-94bb-515be61ef2d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_ba79696d-830b-44fc-94bb-515be61ef2d9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_NoncontrollingInterestDecreaseFromRemeasurement_68bace10-593c-4919-934e-74f484582a9f" xlink:href="flnc-20221231.xsd#flnc_NoncontrollingInterestDecreaseFromRemeasurement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_flnc_NoncontrollingInterestDecreaseFromRemeasurement_68bace10-593c-4919-934e-74f484582a9f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_f844dda7-8972-4889-bd11-2ad66f94f1ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_f844dda7-8972-4889-bd11-2ad66f94f1ba" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_8d7d7458-2045-4304-8215-dcabd558b71e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_8d7d7458-2045-4304-8215-dcabd558b71e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_706ca0e7-9fef-40a6-be10-121f2a8f375d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_706ca0e7-9fef-40a6-be10-121f2a8f375d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ee1f24b7-cd74-493d-99c3-ddc9d9d8317e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ee1f24b7-cd74-493d-99c3-ddc9d9d8317e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_bf732baa-70a5-4d55-9c13-329cc874df4a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_bf732baa-70a5-4d55-9c13-329cc874df4a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_e52ef92a-1dbf-4248-883e-85a38e5b4f64" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_e52ef92a-1dbf-4248-883e-85a38e5b4f64" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_319d4852-d586-4d1b-94f4-f6f2119305ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_319d4852-d586-4d1b-94f4-f6f2119305ec" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_6f8fae78-1d60-4061-aac5-6f9940342fad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f2305940-6ca8-41b1-9609-545ffa748001" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_6f8fae78-1d60-4061-aac5-6f9940342fad" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_a623eac1-b55f-49ab-aa5d-16ec02f4c830" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_5dc8aa87-c489-4aa6-85a6-8d0fdc539661" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_9d5576cb-6b3a-4769-ab58-60e0774552cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MembersEquity_3a9463db-af15-47b6-9e43-591b54ea7237" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MembersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_b4ac2016-b939-4501-b238-f1b2a8337dc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4a6f3170-fa66-4e29-9cbb-f41fc360d0bc" xlink:to="loc_us-gaap_StatementTable_b4ac2016-b939-4501-b238-f1b2a8337dc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_16f96312-264e-4918-8ef0-9405ffb9fa2d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b4ac2016-b939-4501-b238-f1b2a8337dc8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_16f96312-264e-4918-8ef0-9405ffb9fa2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_16f96312-264e-4918-8ef0-9405ffb9fa2d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_16f96312-264e-4918-8ef0-9405ffb9fa2d" xlink:to="loc_us-gaap_EquityComponentDomain_16f96312-264e-4918-8ef0-9405ffb9fa2d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_16f96312-264e-4918-8ef0-9405ffb9fa2d" xlink:to="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MemberUnitsMember_1faf509c-97d7-4f00-a414-42c7124fbc8b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MemberUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_MemberUnitsMember_1faf509c-97d7-4f00-a414-42c7124fbc8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_d0f8899b-212d-40af-941e-88f83c9b7309" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_CommonStockMember_d0f8899b-212d-40af-941e-88f83c9b7309" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_20395948-4e01-4e45-af1e-e5cccbb7d4dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_20395948-4e01-4e45-af1e-e5cccbb7d4dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_fb60ac47-9e15-4633-b2f4-706355fbc097" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_RetainedEarningsMember_fb60ac47-9e15-4633-b2f4-706355fbc097" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_151c9e96-0676-4c11-b84a-75c1c073650b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_151c9e96-0676-4c11-b84a-75c1c073650b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_7a9c2a12-1de4-4b1d-827c-0b83b7a11f17" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_TreasuryStockCommonMember_7a9c2a12-1de4-4b1d-827c-0b83b7a11f17" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_b97c42b2-5461-4d82-80d8-a599ac89f066" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_63b40b09-645f-495f-9fd3-dbd442bd6d2d" xlink:to="loc_us-gaap_NoncontrollingInterestMember_b97c42b2-5461-4d82-80d8-a599ac89f066" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_d63bd906-30fb-45d5-a0bb-2c95e6da7854" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b4ac2016-b939-4501-b238-f1b2a8337dc8" xlink:to="loc_us-gaap_StatementClassOfStockAxis_d63bd906-30fb-45d5-a0bb-2c95e6da7854" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d63bd906-30fb-45d5-a0bb-2c95e6da7854_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d63bd906-30fb-45d5-a0bb-2c95e6da7854" xlink:to="loc_us-gaap_ClassOfStockDomain_d63bd906-30fb-45d5-a0bb-2c95e6da7854_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_739d5e90-2e2f-4db8-8fb9-390ea75b17a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d63bd906-30fb-45d5-a0bb-2c95e6da7854" xlink:to="loc_us-gaap_ClassOfStockDomain_739d5e90-2e2f-4db8-8fb9-390ea75b17a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_a03cade9-984c-4362-be5d-6ffccc1b78f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_739d5e90-2e2f-4db8-8fb9-390ea75b17a5" xlink:to="loc_us-gaap_CommonClassAMember_a03cade9-984c-4362-be5d-6ffccc1b78f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_f615347e-1743-4b1c-9559-ec60f8771a42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_739d5e90-2e2f-4db8-8fb9-390ea75b17a5" xlink:to="loc_us-gaap_CommonClassBMember_f615347e-1743-4b1c-9559-ec60f8771a42" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesNoncontrollingInterestDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#SummaryofSignificantAccountingPoliciesandEstimatesNoncontrollingInterestDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesNoncontrollingInterestDetails" xlink:type="extended" id="icf2a96e25b9f40f5b619161b3bf3f22b_SummaryofSignificantAccountingPoliciesandEstimatesNoncontrollingInterestDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_b98b8bcc-acb6-49c8-8210-71df1c7fb7ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_842ccc77-c45e-4913-b50a-3124f210aae7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_b98b8bcc-acb6-49c8-8210-71df1c7fb7ce" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_842ccc77-c45e-4913-b50a-3124f210aae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_27455c39-60a0-4de2-b38d-35090595adb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_b98b8bcc-acb6-49c8-8210-71df1c7fb7ce" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_27455c39-60a0-4de2-b38d-35090595adb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_cbc076ab-d875-422f-a061-bbf30bc30c9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_b98b8bcc-acb6-49c8-8210-71df1c7fb7ce" xlink:to="loc_us-gaap_MinorityInterestTable_cbc076ab-d875-422f-a061-bbf30bc30c9d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_045f12b7-6a50-4055-b9a8-019730a8b720" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_cbc076ab-d875-422f-a061-bbf30bc30c9d" xlink:to="loc_srt_OwnershipAxis_045f12b7-6a50-4055-b9a8-019730a8b720" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_045f12b7-6a50-4055-b9a8-019730a8b720_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_045f12b7-6a50-4055-b9a8-019730a8b720" xlink:to="loc_srt_OwnershipDomain_045f12b7-6a50-4055-b9a8-019730a8b720_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_fb393c26-42f8-4405-abee-8153ac17012a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_045f12b7-6a50-4055-b9a8-019730a8b720" xlink:to="loc_srt_OwnershipDomain_fb393c26-42f8-4405-abee-8153ac17012a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_FluenceEnergyLLCMember_67448ae0-b9cf-40d3-990b-74631496ac63" xlink:href="flnc-20221231.xsd#flnc_FluenceEnergyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_fb393c26-42f8-4405-abee-8153ac17012a" xlink:to="loc_flnc_FluenceEnergyLLCMember_67448ae0-b9cf-40d3-990b-74631496ac63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_AESGridStabilityLLCMember_f59a277d-a2f3-43fc-9da2-8c7274b0a4cc" xlink:href="flnc-20221231.xsd#flnc_AESGridStabilityLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_fb393c26-42f8-4405-abee-8153ac17012a" xlink:to="loc_flnc_AESGridStabilityLLCMember_f59a277d-a2f3-43fc-9da2-8c7274b0a4cc" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesCashRestrictionsDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#SummaryofSignificantAccountingPoliciesandEstimatesCashRestrictionsDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesCashRestrictionsDetails" xlink:type="extended" id="i18c4c281013f45a3b27d91fbc2ed380e_SummaryofSignificantAccountingPoliciesandEstimatesCashRestrictionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsLineItems_e263aed3-47d1-45a6-99fb-60b93fc3c2a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_f240bce8-4bc7-47da-9e16-acb7d5de4142" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_e263aed3-47d1-45a6-99fb-60b93fc3c2a2" xlink:to="loc_us-gaap_RestrictedCashCurrent_f240bce8-4bc7-47da-9e16-acb7d5de4142" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_38ec72c9-cba2-4312-b0ed-4306096e289b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_e263aed3-47d1-45a6-99fb-60b93fc3c2a2" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_38ec72c9-cba2-4312-b0ed-4306096e289b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_ba8d27cb-498c-4590-a908-e6adb2556f38" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_e263aed3-47d1-45a6-99fb-60b93fc3c2a2" xlink:to="loc_us-gaap_RestrictedCash_ba8d27cb-498c-4590-a908-e6adb2556f38" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_cbbf2d25-485c-46d6-b3a3-86806dc9a6b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_e263aed3-47d1-45a6-99fb-60b93fc3c2a2" xlink:to="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_cbbf2d25-485c-46d6-b3a3-86806dc9a6b3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_4e8eb83b-0115-413a-9459-56d7077f4667" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_cbbf2d25-485c-46d6-b3a3-86806dc9a6b3" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_4e8eb83b-0115-413a-9459-56d7077f4667" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4e8eb83b-0115-413a-9459-56d7077f4667_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_4e8eb83b-0115-413a-9459-56d7077f4667" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4e8eb83b-0115-413a-9459-56d7077f4667_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_ce666c19-ea01-4809-b6e8-07760860ddf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_4e8eb83b-0115-413a-9459-56d7077f4667" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_ce666c19-ea01-4809-b6e8-07760860ddf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CreditCardProgramCollateralMember_16ca85c0-85be-4181-9233-9528efbb9355" xlink:href="flnc-20221231.xsd#flnc_CreditCardProgramCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_ce666c19-ea01-4809-b6e8-07760860ddf4" xlink:to="loc_flnc_CreditCardProgramCollateralMember_16ca85c0-85be-4181-9233-9528efbb9355" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_OutstandingBankGuaranteeCollateralMember_9a3d2a4b-8679-4014-9e62-fee868f51bb7" xlink:href="flnc-20221231.xsd#flnc_OutstandingBankGuaranteeCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_ce666c19-ea01-4809-b6e8-07760860ddf4" xlink:to="loc_flnc_OutstandingBankGuaranteeCollateralMember_9a3d2a4b-8679-4014-9e62-fee868f51bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_SuretyProgramCollateralMember_29949056-d4db-4388-89db-3aac0f0876a2" xlink:href="flnc-20221231.xsd#flnc_SuretyProgramCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_ce666c19-ea01-4809-b6e8-07760860ddf4" xlink:to="loc_flnc_SuretyProgramCollateralMember_29949056-d4db-4388-89db-3aac0f0876a2" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesSupplyChainFinancingDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#SummaryofSignificantAccountingPoliciesandEstimatesSupplyChainFinancingDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesSupplyChainFinancingDetails" xlink:type="extended" id="if41d1add8a964830becc64fc44c9e4cc_SummaryofSignificantAccountingPoliciesandEstimatesSupplyChainFinancingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_923792a8-e9a2-4359-94aa-013d9f9cfb9b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_SupplyChainFinancingGuaranteeByRelatedParty_21c10dc0-4a84-40fc-b31e-b5bb39e3f8cb" xlink:href="flnc-20221231.xsd#flnc_SupplyChainFinancingGuaranteeByRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_923792a8-e9a2-4359-94aa-013d9f9cfb9b" xlink:to="loc_flnc_SupplyChainFinancingGuaranteeByRelatedParty_21c10dc0-4a84-40fc-b31e-b5bb39e3f8cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_1271df5f-a93a-4a84-962e-e43d7cbc93ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_923792a8-e9a2-4359-94aa-013d9f9cfb9b" xlink:to="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_1271df5f-a93a-4a84-962e-e43d7cbc93ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_37e2396b-d620-4283-8c12-89847c49251e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_923792a8-e9a2-4359-94aa-013d9f9cfb9b" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_37e2396b-d620-4283-8c12-89847c49251e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_92e54fd8-835b-461c-9042-bd1f68338fe9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_37e2396b-d620-4283-8c12-89847c49251e" xlink:to="loc_srt_CounterpartyNameAxis_92e54fd8-835b-461c-9042-bd1f68338fe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_92e54fd8-835b-461c-9042-bd1f68338fe9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_92e54fd8-835b-461c-9042-bd1f68338fe9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_92e54fd8-835b-461c-9042-bd1f68338fe9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b78d5605-9931-422f-b472-16a41ba4bcf7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_92e54fd8-835b-461c-9042-bd1f68338fe9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b78d5605-9931-422f-b472-16a41ba4bcf7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_AESGridStabilityLLCMember_c9209961-a8db-4ded-be3e-2062a07306e8" xlink:href="flnc-20221231.xsd#flnc_AESGridStabilityLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b78d5605-9931-422f-b472-16a41ba4bcf7" xlink:to="loc_flnc_AESGridStabilityLLCMember_c9209961-a8db-4ded-be3e-2062a07306e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_SiemensIndustryIncMember_39586123-5366-47b9-88dc-87b72f9b3e66" xlink:href="flnc-20221231.xsd#flnc_SiemensIndustryIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b78d5605-9931-422f-b472-16a41ba4bcf7" xlink:to="loc_flnc_SiemensIndustryIncMember_39586123-5366-47b9-88dc-87b72f9b3e66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ThreeSupplyChainFinancingSuppliersMember_de30506d-7a1e-4b57-8612-fed7be94c824" xlink:href="flnc-20221231.xsd#flnc_ThreeSupplyChainFinancingSuppliersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b78d5605-9931-422f-b472-16a41ba4bcf7" xlink:to="loc_flnc_ThreeSupplyChainFinancingSuppliersMember_de30506d-7a1e-4b57-8612-fed7be94c824" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_246d9b99-43cf-4616-8fe8-24ba4b6246db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_37e2396b-d620-4283-8c12-89847c49251e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_246d9b99-43cf-4616-8fe8-24ba4b6246db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_246d9b99-43cf-4616-8fe8-24ba4b6246db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_246d9b99-43cf-4616-8fe8-24ba4b6246db" xlink:to="loc_us-gaap_RelatedPartyDomain_246d9b99-43cf-4616-8fe8-24ba4b6246db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_f5785637-25c8-4d3e-9131-75e9ad67bd03" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_246d9b99-43cf-4616-8fe8-24ba4b6246db" xlink:to="loc_us-gaap_RelatedPartyDomain_f5785637-25c8-4d3e-9131-75e9ad67bd03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_c29590b0-991c-4115-a6bc-783b6135725b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_f5785637-25c8-4d3e-9131-75e9ad67bd03" xlink:to="loc_srt_AffiliatedEntityMember_c29590b0-991c-4115-a6bc-783b6135725b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesDilutiveSecuritiesDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#SummaryofSignificantAccountingPoliciesandEstimatesDilutiveSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/SummaryofSignificantAccountingPoliciesandEstimatesDilutiveSecuritiesDetails" xlink:type="extended" id="i2430cb12b49047f5bb16162943584684_SummaryofSignificantAccountingPoliciesandEstimatesDilutiveSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_139a888b-df9d-4a88-8620-415c0e8dbe8f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_542828a1-93f9-4d67-b5d9-ad96e13b91d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_139a888b-df9d-4a88-8620-415c0e8dbe8f" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_542828a1-93f9-4d67-b5d9-ad96e13b91d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_221f4375-5fb6-4b31-b07b-10cb932b453c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_139a888b-df9d-4a88-8620-415c0e8dbe8f" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_221f4375-5fb6-4b31-b07b-10cb932b453c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_221f4375-5fb6-4b31-b07b-10cb932b453c" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c2fe9e6b-5fe9-49b9-a5ec-c37952534d9e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB1Member_408f6429-7356-48fd-86b5-4f0aa5672411" xlink:href="flnc-20221231.xsd#flnc_CommonClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:to="loc_flnc_CommonClassB1Member_408f6429-7356-48fd-86b5-4f0aa5672411" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_8278c168-3e9e-46e3-9b83-e3322de371ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:to="loc_us-gaap_EmployeeStockOptionMember_8278c168-3e9e-46e3-9b83-e3322de371ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_9abad90c-ab8a-4a43-a857-de3e1f2d6ae1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_9abad90c-ab8a-4a43-a857-de3e1f2d6ae1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_d1f563e9-5298-4d0e-9668-d376a80b79f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_93fa413c-d32b-4724-a316-d57f97fd0cf8" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_d1f563e9-5298-4d0e-9668-d376a80b79f9" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RevenuefromContractswithCustomersRevenuebyContractsDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RevenuefromContractswithCustomersRevenuebyContractsDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RevenuefromContractswithCustomersRevenuebyContractsDetails" xlink:type="extended" id="ia0d420374de44b40977e87b695c823cc_RevenuefromContractswithCustomersRevenuebyContractsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_83ddd3e4-a714-4fc4-b0d0-c39c7b0d368d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c7977455-2e23-4d13-b46d-4e65358871d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_83ddd3e4-a714-4fc4-b0d0-c39c7b0d368d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c7977455-2e23-4d13-b46d-4e65358871d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_b8f49c0d-fff3-4855-8d92-1120472091fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_83ddd3e4-a714-4fc4-b0d0-c39c7b0d368d" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_b8f49c0d-fff3-4855-8d92-1120472091fa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_720c395e-85b2-4767-b09a-610b2def42af" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_b8f49c0d-fff3-4855-8d92-1120472091fa" xlink:to="loc_srt_ProductOrServiceAxis_720c395e-85b2-4767-b09a-610b2def42af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_720c395e-85b2-4767-b09a-610b2def42af_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_720c395e-85b2-4767-b09a-610b2def42af" xlink:to="loc_srt_ProductsAndServicesDomain_720c395e-85b2-4767-b09a-610b2def42af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_720c395e-85b2-4767-b09a-610b2def42af" xlink:to="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_ac15be51-9338-48e5-a4ac-67517adb7610" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:to="loc_us-gaap_ProductMember_ac15be51-9338-48e5-a4ac-67517adb7610" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_0cc036a2-b9f1-44c6-8551-470006a7b881" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:to="loc_us-gaap_ServiceOtherMember_0cc036a2-b9f1-44c6-8551-470006a7b881" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ServicesDigitalApplicationsAndSolutionsMember_7e3927d2-5f3a-4017-ad72-dd6b262ab067" xlink:href="flnc-20221231.xsd#flnc_ServicesDigitalApplicationsAndSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:to="loc_flnc_ServicesDigitalApplicationsAndSolutionsMember_7e3927d2-5f3a-4017-ad72-dd6b262ab067" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_18fcc3c6-60d8-4aa1-b6d0-f01f381860de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7c65f09-d097-4fe2-b734-2e891d3c0b9f" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_18fcc3c6-60d8-4aa1-b6d0-f01f381860de" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RevenuefromContractswithCustomersGeographicalRegionsDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RevenuefromContractswithCustomersGeographicalRegionsDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RevenuefromContractswithCustomersGeographicalRegionsDetails" xlink:type="extended" id="i9f71e99f21bd47dab4a3cf952fbbdcf0_RevenuefromContractswithCustomersGeographicalRegionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_e0e3a710-677c-4f4a-8ada-8b5f58047d96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_02686212-e0a3-4d0b-b97f-280e415a4bf6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0e3a710-677c-4f4a-8ada-8b5f58047d96" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_02686212-e0a3-4d0b-b97f-280e415a4bf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_a3a0211e-4125-49aa-978f-bb6c7115745f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0e3a710-677c-4f4a-8ada-8b5f58047d96" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_a3a0211e-4125-49aa-978f-bb6c7115745f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_55351115-d4df-4716-9abc-4fcea08345c7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a3a0211e-4125-49aa-978f-bb6c7115745f" xlink:to="loc_srt_StatementGeographicalAxis_55351115-d4df-4716-9abc-4fcea08345c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_55351115-d4df-4716-9abc-4fcea08345c7_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_55351115-d4df-4716-9abc-4fcea08345c7" xlink:to="loc_srt_SegmentGeographicalDomain_55351115-d4df-4716-9abc-4fcea08345c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_d49807b7-02ae-4b4c-926e-ed856a4b9d8d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_55351115-d4df-4716-9abc-4fcea08345c7" xlink:to="loc_srt_SegmentGeographicalDomain_d49807b7-02ae-4b4c-926e-ed856a4b9d8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_51c964ab-0c74-47e0-a188-0b37202c32b1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d49807b7-02ae-4b4c-926e-ed856a4b9d8d" xlink:to="loc_srt_AmericasMember_51c964ab-0c74-47e0-a188-0b37202c32b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_c37efcb3-1c67-4694-8166-4d09352adbec" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d49807b7-02ae-4b4c-926e-ed856a4b9d8d" xlink:to="loc_srt_AsiaPacificMember_c37efcb3-1c67-4694-8166-4d09352adbec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_c5e23517-b9da-4180-8928-66ceed7b831c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d49807b7-02ae-4b4c-926e-ed856a4b9d8d" xlink:to="loc_us-gaap_EMEAMember_c5e23517-b9da-4180-8928-66ceed7b831c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RevenuefromContractswithCustomersContractLiabilityDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RevenuefromContractswithCustomersContractLiabilityDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RevenuefromContractswithCustomersContractLiabilityDetails" xlink:type="extended" id="i6487eb00821a424392b0bcbc9aa74a8f_RevenuefromContractswithCustomersContractLiabilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ConsolidatedEntitiesLineItems_7b4893b6-d634-4e22-a3f2-745daa3a24b9" xlink:href="flnc-20221231.xsd#flnc_ConsolidatedEntitiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ContractWithCustomerLiabilityRollForward_3c0da51d-0d7c-4459-a22c-a59235ce9f80" xlink:href="flnc-20221231.xsd#flnc_ContractWithCustomerLiabilityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_ConsolidatedEntitiesLineItems_7b4893b6-d634-4e22-a3f2-745daa3a24b9" xlink:to="loc_flnc_ContractWithCustomerLiabilityRollForward_3c0da51d-0d7c-4459-a22c-a59235ce9f80" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_c55bb0be-3946-438f-85cc-b70f1ebc813c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_ContractWithCustomerLiabilityRollForward_3c0da51d-0d7c-4459-a22c-a59235ce9f80" xlink:to="loc_us-gaap_ContractWithCustomerLiability_c55bb0be-3946-438f-85cc-b70f1ebc813c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ContractWithCustomerLiabilityAdditions_447b4d44-9992-4761-a6ac-aaa7c6452bc8" xlink:href="flnc-20221231.xsd#flnc_ContractWithCustomerLiabilityAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_ContractWithCustomerLiabilityRollForward_3c0da51d-0d7c-4459-a22c-a59235ce9f80" xlink:to="loc_flnc_ContractWithCustomerLiabilityAdditions_447b4d44-9992-4761-a6ac-aaa7c6452bc8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01ac6e1d-b15e-43f7-9f60-480dcee99aa9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_ContractWithCustomerLiabilityRollForward_3c0da51d-0d7c-4459-a22c-a59235ce9f80" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01ac6e1d-b15e-43f7-9f60-480dcee99aa9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_4f6ac0e5-fe9b-4726-ad9d-ae765f9bf44c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ConsolidatedEntitiesTable_5cff7aef-25e2-44f0-873b-2c37f6792276" xlink:href="flnc-20221231.xsd#flnc_ConsolidatedEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_flnc_ConsolidatedEntitiesLineItems_7b4893b6-d634-4e22-a3f2-745daa3a24b9" xlink:to="loc_flnc_ConsolidatedEntitiesTable_5cff7aef-25e2-44f0-873b-2c37f6792276" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_4b7f0889-a287-4442-bb50-2f1bd9001554" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_flnc_ConsolidatedEntitiesTable_5cff7aef-25e2-44f0-873b-2c37f6792276" xlink:to="loc_srt_ConsolidatedEntitiesAxis_4b7f0889-a287-4442-bb50-2f1bd9001554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_4b7f0889-a287-4442-bb50-2f1bd9001554_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_4b7f0889-a287-4442-bb50-2f1bd9001554" xlink:to="loc_srt_ConsolidatedEntitiesDomain_4b7f0889-a287-4442-bb50-2f1bd9001554_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_fd65234d-61aa-4d10-b187-5eb36a5d2f63" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_4b7f0889-a287-4442-bb50-2f1bd9001554" xlink:to="loc_srt_ConsolidatedEntitiesDomain_fd65234d-61aa-4d10-b187-5eb36a5d2f63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember_aac164d5-957f-4611-a625-52009ce9c7bf" xlink:href="flnc-20221231.xsd#flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_fd65234d-61aa-4d10-b187-5eb36a5d2f63" xlink:to="loc_flnc_ConsolidatedEntitiesExcludingAffiliatedEntitiesMember_aac164d5-957f-4611-a625-52009ce9c7bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_760c436d-eb4b-47ac-842e-715df403334d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_fd65234d-61aa-4d10-b187-5eb36a5d2f63" xlink:to="loc_srt_AffiliatedEntityMember_760c436d-eb4b-47ac-842e-715df403334d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RevenuefromContractswithCustomersAdditionalInformationDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RevenuefromContractswithCustomersAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RevenuefromContractswithCustomersAdditionalInformationDetails" xlink:type="extended" id="i5f4b60a0f6644ba09ffa67508f50db50_RevenuefromContractswithCustomersAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_4bd4af9c-1ff7-4609-8d81-8f0a6d28aa3e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_4bd4af9c-1ff7-4609-8d81-8f0a6d28aa3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_106a70ae-783f-4551-9c75-62122b5b72d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_106a70ae-783f-4551-9c75-62122b5b72d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4f63fe59-9ccd-499d-98c9-690fcd6c3b00" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4f63fe59-9ccd-499d-98c9-690fcd6c3b00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_85e273f8-a211-42a0-98d7-1ef93bb6f666" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_85e273f8-a211-42a0-98d7-1ef93bb6f666" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice_40403650-feaa-475f-98bc-e456f919f11e" xlink:href="flnc-20221231.xsd#flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice_40403650-feaa-475f-98bc-e456f919f11e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_e55db496-e503-4cce-a024-54202fb49f99" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_e55db496-e503-4cce-a024-54202fb49f99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_58ed60d0-d21a-4d6b-9757-c3434ec4aca1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_58ed60d0-d21a-4d6b-9757-c3434ec4aca1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_9924c619-589b-4c8f-8187-bdaae7f2ac21" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:to="loc_us-gaap_SalesRevenueNetMember_9924c619-589b-4c8f-8187-bdaae7f2ac21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_27c3da43-0f02-466d-a7aa-06acee49303b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_27c3da43-0f02-466d-a7aa-06acee49303b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_0a297022-3007-484b-9b7b-e7e6e86f8bac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_0a297022-3007-484b-9b7b-e7e6e86f8bac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_d8251281-185d-406c-9534-37a5be659aac_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:to="loc_srt_NameOfMajorCustomerDomain_d8251281-185d-406c-9534-37a5be659aac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:to="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_TwoCustomersMember_6ba2de9c-e896-41ab-bde3-fbf4afecf2cb" xlink:href="flnc-20221231.xsd#flnc_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:to="loc_flnc_TwoCustomersMember_6ba2de9c-e896-41ab-bde3-fbf4afecf2cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_OneCustomerMember_0ee13ed9-7dbf-4fc2-8e0e-77ead4275aaa" xlink:href="flnc-20221231.xsd#flnc_OneCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:to="loc_flnc_OneCustomerMember_0ee13ed9-7dbf-4fc2-8e0e-77ead4275aaa" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RevenuefromContractswithCustomersAdditionalInformationDetails_1" xlink:type="simple" xlink:href="flnc-20221231.xsd#RevenuefromContractswithCustomersAdditionalInformationDetails_1"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RevenuefromContractswithCustomersAdditionalInformationDetails_1" xlink:type="extended" id="i9dfd45934eea44dd91c0c61545a23548_RevenuefromContractswithCustomersAdditionalInformationDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_4bd4af9c-1ff7-4609-8d81-8f0a6d28aa3e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_4bd4af9c-1ff7-4609-8d81-8f0a6d28aa3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_106a70ae-783f-4551-9c75-62122b5b72d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_106a70ae-783f-4551-9c75-62122b5b72d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4f63fe59-9ccd-499d-98c9-690fcd6c3b00" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4f63fe59-9ccd-499d-98c9-690fcd6c3b00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_85e273f8-a211-42a0-98d7-1ef93bb6f666" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_85e273f8-a211-42a0-98d7-1ef93bb6f666" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice_40403650-feaa-475f-98bc-e456f919f11e" xlink:href="flnc-20221231.xsd#flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_flnc_ContractWithCustomerCumulativeAdjustmentForChangeInEstimateOfTransactionPrice_40403650-feaa-475f-98bc-e456f919f11e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6725d939-3e98-46c6-b941-b3571977f0c6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_58ed60d0-d21a-4d6b-9757-c3434ec4aca1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_58ed60d0-d21a-4d6b-9757-c3434ec4aca1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_58ed60d0-d21a-4d6b-9757-c3434ec4aca1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_9924c619-589b-4c8f-8187-bdaae7f2ac21" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b19b06b8-9c0b-474f-8ab8-06cab4872aba" xlink:to="loc_us-gaap_SalesRevenueNetMember_9924c619-589b-4c8f-8187-bdaae7f2ac21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_27c3da43-0f02-466d-a7aa-06acee49303b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_27c3da43-0f02-466d-a7aa-06acee49303b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_27c3da43-0f02-466d-a7aa-06acee49303b" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_0a297022-3007-484b-9b7b-e7e6e86f8bac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_0dd8de94-b96a-49e2-b0ec-e471fbe9962c" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_0a297022-3007-484b-9b7b-e7e6e86f8bac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_124ff039-19c5-4761-9ee8-90443563d361" xlink:to="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_d8251281-185d-406c-9534-37a5be659aac_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:to="loc_srt_NameOfMajorCustomerDomain_d8251281-185d-406c-9534-37a5be659aac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_d8251281-185d-406c-9534-37a5be659aac" xlink:to="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_TwoCustomersMember_6ba2de9c-e896-41ab-bde3-fbf4afecf2cb" xlink:href="flnc-20221231.xsd#flnc_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:to="loc_flnc_TwoCustomersMember_6ba2de9c-e896-41ab-bde3-fbf4afecf2cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_OneCustomerMember_0ee13ed9-7dbf-4fc2-8e0e-77ead4275aaa" xlink:href="flnc-20221231.xsd#flnc_OneCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_66afdba9-185b-4b0b-80c3-6a8d43e23f97" xlink:to="loc_flnc_OneCustomerMember_0ee13ed9-7dbf-4fc2-8e0e-77ead4275aaa" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/InventoryNetDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#InventoryNetDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/InventoryNetDetails" xlink:type="extended" id="i5d104335894a464daaf02f037a3a7666_InventoryNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_cfacf26b-8e42-4fed-a7f0-d2c0916faad0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_d5de7b84-dba2-43b2-bc9a-d84b45044118" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_cfacf26b-8e42-4fed-a7f0-d2c0916faad0" xlink:to="loc_us-gaap_InventoryGross_d5de7b84-dba2-43b2-bc9a-d84b45044118" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryValuationReserves_c98f7cdb-710b-4288-b42d-7ee4eb8d3140" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryValuationReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_cfacf26b-8e42-4fed-a7f0-d2c0916faad0" xlink:to="loc_us-gaap_InventoryValuationReserves_c98f7cdb-710b-4288-b42d-7ee4eb8d3140" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_99ec151b-89ca-4145-a7e1-b76f4a682ba6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_cfacf26b-8e42-4fed-a7f0-d2c0916faad0" xlink:to="loc_us-gaap_InventoryNet_99ec151b-89ca-4145-a7e1-b76f4a682ba6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_48ec9cd6-7aa7-488d-aa37-801b98c1c309" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_cfacf26b-8e42-4fed-a7f0-d2c0916faad0" xlink:to="loc_us-gaap_InventoryCurrentTable_48ec9cd6-7aa7-488d-aa37-801b98c1c309" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryAxis_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_48ec9cd6-7aa7-488d-aa37-801b98c1c309" xlink:to="loc_us-gaap_PublicUtilitiesInventoryAxis_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_3fbd918d-13b3-488a-8335-bb4af5d8b66d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_6105fc6d-b7e7-459b-93d3-c8a9e3ca35b0" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_3fbd918d-13b3-488a-8335-bb4af5d8b66d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CubesBatteriesAndOtherEquipmentMember_3e8586d8-3247-4f32-a776-20865e8a786f" xlink:href="flnc-20221231.xsd#flnc_CubesBatteriesAndOtherEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_3fbd918d-13b3-488a-8335-bb4af5d8b66d" xlink:to="loc_flnc_CubesBatteriesAndOtherEquipmentMember_3e8586d8-3247-4f32-a776-20865e8a786f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ShippingContainersAndSparePartsMember_21452561-38af-4fd8-b4d6-ce84a87b1642" xlink:href="flnc-20221231.xsd#flnc_ShippingContainersAndSparePartsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_3fbd918d-13b3-488a-8335-bb4af5d8b66d" xlink:to="loc_flnc_ShippingContainersAndSparePartsMember_21452561-38af-4fd8-b4d6-ce84a87b1642" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/IntangibleAssetsNetDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#IntangibleAssetsNetDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/IntangibleAssetsNetDetails" xlink:type="extended" id="if1bb99c68ba44d268387d6d8c36731b4_IntangibleAssetsNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_2f50cbf1-768e-4fe5-b837-fbf858f1aa5a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_2f50cbf1-768e-4fe5-b837-fbf858f1aa5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_84def1c3-6511-4c09-ae83-2f5270db8eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_84def1c3-6511-4c09-ae83-2f5270db8eb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_638b2e57-7982-411c-b64e-f5fc53958488" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_638b2e57-7982-411c-b64e-f5fc53958488" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_6f6a58d2-df33-4982-a4bf-29ac8adf4e73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_6f6a58d2-df33-4982-a4bf-29ac8adf4e73" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_bf173778-f149-4b86-bdb9-b2d44d03e28f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_fb8316c4-3834-4f95-a484-4b2a5a859b12" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_bf173778-f149-4b86-bdb9-b2d44d03e28f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_eab6bc79-9316-40e1-a1f1-acbf5ce10d50" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_bf173778-f149-4b86-bdb9-b2d44d03e28f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_eab6bc79-9316-40e1-a1f1-acbf5ce10d50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_eab6bc79-9316-40e1-a1f1-acbf5ce10d50_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_eab6bc79-9316-40e1-a1f1-acbf5ce10d50" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_eab6bc79-9316-40e1-a1f1-acbf5ce10d50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_eab6bc79-9316-40e1-a1f1-acbf5ce10d50" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_PatentsAndLicensingAgreementsMember_fd8bffe3-c3d6-4c2d-bd8e-310c63cccc79" xlink:href="flnc-20221231.xsd#flnc_PatentsAndLicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:to="loc_flnc_PatentsAndLicensingAgreementsMember_fd8bffe3-c3d6-4c2d-bd8e-310c63cccc79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_52d2cc13-7186-4e84-b3e2-68bd38b5a7e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_52d2cc13-7186-4e84-b3e2-68bd38b5a7e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_271dfb42-fd0e-488e-96ed-485f8cd05d33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:to="loc_us-gaap_CustomerRelationshipsMember_271dfb42-fd0e-488e-96ed-485f8cd05d33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_426e3dca-46eb-4f94-9c51-72da1f6543e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_426e3dca-46eb-4f94-9c51-72da1f6543e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_19574b99-eee6-4487-8d67-b06547ef8469" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d86564b7-3bae-4f9f-959e-adc276db2eed" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_19574b99-eee6-4487-8d67-b06547ef8469" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/DebtRevolvingCreditFacilityDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#DebtRevolvingCreditFacilityDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/DebtRevolvingCreditFacilityDetails" xlink:type="extended" id="i14eabccb89ee4349bced83e81dd7da05_DebtRevolvingCreditFacilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_e9d1bcdd-ece6-40cd-9339-b336d1869308" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_e9d1bcdd-ece6-40cd-9339-b336d1869308" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LineOfCreditFacilityNumberOfOtherBanksIncludedInLendersParty_77926cf0-56cd-4d7b-8e81-288c9c937323" xlink:href="flnc-20221231.xsd#flnc_LineOfCreditFacilityNumberOfOtherBanksIncludedInLendersParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_LineOfCreditFacilityNumberOfOtherBanksIncludedInLendersParty_77926cf0-56cd-4d7b-8e81-288c9c937323" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LineOfCreditFacilityIncreaseInBorrowingCapacity_868a4674-1f29-4b5e-a4a9-d5d2a23ad94f" xlink:href="flnc-20221231.xsd#flnc_LineOfCreditFacilityIncreaseInBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_LineOfCreditFacilityIncreaseInBorrowingCapacity_868a4674-1f29-4b5e-a4a9-d5d2a23ad94f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_c47362e0-916b-48c9-aff3-84a6191e5a77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_c47362e0-916b-48c9-aff3-84a6191e5a77" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_71c91099-55f2-44be-a69b-cb04de25959e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_71c91099-55f2-44be-a69b-cb04de25959e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_199661bc-02a2-4a8c-aef7-40bd9a804b15" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_199661bc-02a2-4a8c-aef7-40bd9a804b15" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_DebtInstrumentCovenantInvestmentThresholdMaximum_a799715c-0246-4606-80ee-666401878f20" xlink:href="flnc-20221231.xsd#flnc_DebtInstrumentCovenantInvestmentThresholdMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_DebtInstrumentCovenantInvestmentThresholdMaximum_a799715c-0246-4606-80ee-666401878f20" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_DebtInstrumentCovenantInvestmentThresholdPercentageOfConsolidatedAssetsMaximum_1da06dd4-0a58-4922-b499-f51147ce1d75" xlink:href="flnc-20221231.xsd#flnc_DebtInstrumentCovenantInvestmentThresholdPercentageOfConsolidatedAssetsMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_DebtInstrumentCovenantInvestmentThresholdPercentageOfConsolidatedAssetsMaximum_1da06dd4-0a58-4922-b499-f51147ce1d75" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_DebtInstrumentCovenantTotalLiquidityMaximum_366ec7c3-8bd1-4d56-85a3-3428ac66271e" xlink:href="flnc-20221231.xsd#flnc_DebtInstrumentCovenantTotalLiquidityMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_DebtInstrumentCovenantTotalLiquidityMaximum_366ec7c3-8bd1-4d56-85a3-3428ac66271e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LineOfCreditFacilityFinancialCovenantEBITDAThreshold_9de024f3-5afd-4d59-b0ed-49dd37409e35" xlink:href="flnc-20221231.xsd#flnc_LineOfCreditFacilityFinancialCovenantEBITDAThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_LineOfCreditFacilityFinancialCovenantEBITDAThreshold_9de024f3-5afd-4d59-b0ed-49dd37409e35" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LineOfCreditFacilityFinancialCovenantEBITDAThresholdNumberOfQuarters_abfeec8d-4e43-44ad-89c8-71c2de02e573" xlink:href="flnc-20221231.xsd#flnc_LineOfCreditFacilityFinancialCovenantEBITDAThresholdNumberOfQuarters"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_flnc_LineOfCreditFacilityFinancialCovenantEBITDAThresholdNumberOfQuarters_abfeec8d-4e43-44ad-89c8-71c2de02e573" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_8c8042e1-b4b0-4f24-a916-2e4c83bd67f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCredit_8c8042e1-b4b0-4f24-a916-2e4c83bd67f6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_c2a5e558-979a-4c66-843f-01f091aab548" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_c2a5e558-979a-4c66-843f-01f091aab548" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_9cb7f4d9-7c23-4215-a30b-e995b9e044c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_9cb7f4d9-7c23-4215-a30b-e995b9e044c0" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_9b27abef-6669-4dd3-8afc-951004d9d6d3" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_f4dc0fc9-23d9-4800-9f04-823869074c21" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:to="loc_us-gaap_CreditFacilityAxis_f4dc0fc9-23d9-4800-9f04-823869074c21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_f4dc0fc9-23d9-4800-9f04-823869074c21_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_f4dc0fc9-23d9-4800-9f04-823869074c21" xlink:to="loc_us-gaap_CreditFacilityDomain_f4dc0fc9-23d9-4800-9f04-823869074c21_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_705d6c32-5872-4de8-a730-3128b5ab5948" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_f4dc0fc9-23d9-4800-9f04-823869074c21" xlink:to="loc_us-gaap_CreditFacilityDomain_705d6c32-5872-4de8-a730-3128b5ab5948" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_5971a717-d6e6-4c3b-9143-649109a21062" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_705d6c32-5872-4de8-a730-3128b5ab5948" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_5971a717-d6e6-4c3b-9143-649109a21062" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_62bce071-fc56-4de4-9620-5b74a38fb0e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_705d6c32-5872-4de8-a730-3128b5ab5948" xlink:to="loc_us-gaap_LetterOfCreditMember_62bce071-fc56-4de4-9620-5b74a38fb0e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:to="loc_us-gaap_DebtInstrumentAxis_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_850366cb-c74f-4542-8fa5-46bb6da620d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_148e9333-cb3e-4f70-904a-3fdbe1aa9e3e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_850366cb-c74f-4542-8fa5-46bb6da620d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_TheRevolverMember_12c39a64-c988-4250-b97b-a7480277e7c2" xlink:href="flnc-20221231.xsd#flnc_TheRevolverMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_850366cb-c74f-4542-8fa5-46bb6da620d6" xlink:to="loc_flnc_TheRevolverMember_12c39a64-c988-4250-b97b-a7480277e7c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_8a36e673-6c2e-456a-a029-8301d191943d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_8a36e673-6c2e-456a-a029-8301d191943d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_8a36e673-6c2e-456a-a029-8301d191943d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_8a36e673-6c2e-456a-a029-8301d191943d" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_8a36e673-6c2e-456a-a029-8301d191943d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_67307483-5c90-4c78-a107-e0ce93470d13" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_8a36e673-6c2e-456a-a029-8301d191943d" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_67307483-5c90-4c78-a107-e0ce93470d13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e1a0791f-f068-4d2d-a2b9-17a9b16d755d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_67307483-5c90-4c78-a107-e0ce93470d13" xlink:to="loc_us-gaap_LineOfCreditMember_e1a0791f-f068-4d2d-a2b9-17a9b16d755d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_547bb7ac-fe6d-47e0-a159-a762e909a775" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:to="loc_us-gaap_VariableRateAxis_547bb7ac-fe6d-47e0-a159-a762e909a775" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_547bb7ac-fe6d-47e0-a159-a762e909a775_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_547bb7ac-fe6d-47e0-a159-a762e909a775" xlink:to="loc_us-gaap_VariableRateDomain_547bb7ac-fe6d-47e0-a159-a762e909a775_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_ac078a58-2a4a-489c-ab0a-c7779949c0cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_547bb7ac-fe6d-47e0-a159-a762e909a775" xlink:to="loc_us-gaap_VariableRateDomain_ac078a58-2a4a-489c-ab0a-c7779949c0cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_455ec809-bc91-43c7-93bb-a66c93d00530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_ac078a58-2a4a-489c-ab0a-c7779949c0cb" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_455ec809-bc91-43c7-93bb-a66c93d00530" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_f9e48491-80e9-4f11-a387-83be63f8705b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_ac078a58-2a4a-489c-ab0a-c7779949c0cb" xlink:to="loc_us-gaap_BaseRateMember_f9e48491-80e9-4f11-a387-83be63f8705b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_508024eb-e52a-4a07-a8ac-e3588b70bc73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a75ecea8-61c4-45ba-948e-ef18ae923651" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_508024eb-e52a-4a07-a8ac-e3588b70bc73" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_508024eb-e52a-4a07-a8ac-e3588b70bc73_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_508024eb-e52a-4a07-a8ac-e3588b70bc73" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_508024eb-e52a-4a07-a8ac-e3588b70bc73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_77518d52-e777-4eb7-93a8-8eec2040cfde" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_508024eb-e52a-4a07-a8ac-e3588b70bc73" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_77518d52-e777-4eb7-93a8-8eec2040cfde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_43629849-8379-4ae5-ac93-e7e15ce4ec76" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_77518d52-e777-4eb7-93a8-8eec2040cfde" xlink:to="loc_us-gaap_LineOfCreditMember_43629849-8379-4ae5-ac93-e7e15ce4ec76" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/DebtLineofCreditDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#DebtLineofCreditDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/DebtLineofCreditDetails" xlink:type="extended" id="i68d2b6c953cd4ccc9ef0a9eb58457982_DebtLineofCreditDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6b797cd0-7819-4b38-8b3e-2f3143ad78b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6b797cd0-7819-4b38-8b3e-2f3143ad78b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_2990658d-8423-485a-87df-20a859678e79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:to="loc_us-gaap_LineOfCredit_2990658d-8423-485a-87df-20a859678e79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_9d06e28e-66ba-4d0b-bd8b-c7d091f6225c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_9d06e28e-66ba-4d0b-bd8b-c7d091f6225c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_12d09721-9520-4bf0-b500-cb3598aacd65" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_12d09721-9520-4bf0-b500-cb3598aacd65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_3dca96f3-d2ae-4017-97ab-cc9d5d3edfec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_6c1aad9a-5375-40a5-bb96-b37033dcc515" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_3dca96f3-d2ae-4017-97ab-cc9d5d3edfec" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_6e561da0-efd7-4443-9333-cd00a25546c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dca96f3-d2ae-4017-97ab-cc9d5d3edfec" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_6e561da0-efd7-4443-9333-cd00a25546c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_6e561da0-efd7-4443-9333-cd00a25546c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_6e561da0-efd7-4443-9333-cd00a25546c5" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_6e561da0-efd7-4443-9333-cd00a25546c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_1d6b5b2d-a961-405a-b0e5-4848664b54ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_6e561da0-efd7-4443-9333-cd00a25546c5" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_1d6b5b2d-a961-405a-b0e5-4848664b54ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_853fdd7e-a9d5-4ccb-842d-cd641247578e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_1d6b5b2d-a961-405a-b0e5-4848664b54ec" xlink:to="loc_us-gaap_LineOfCreditMember_853fdd7e-a9d5-4ccb-842d-cd641247578e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_a762f161-9b14-4bca-9616-f5629e86645d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dca96f3-d2ae-4017-97ab-cc9d5d3edfec" xlink:to="loc_us-gaap_DebtInstrumentAxis_a762f161-9b14-4bca-9616-f5629e86645d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a762f161-9b14-4bca-9616-f5629e86645d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_a762f161-9b14-4bca-9616-f5629e86645d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a762f161-9b14-4bca-9616-f5629e86645d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0632a925-ef17-402d-8ece-5b12c1e7220e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_a762f161-9b14-4bca-9616-f5629e86645d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0632a925-ef17-402d-8ece-5b12c1e7220e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_UncommittedLineOfCreditAgreementMember_3be5c8d0-01fe-4ea0-8fd4-d542728e18f5" xlink:href="flnc-20221231.xsd#flnc_UncommittedLineOfCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0632a925-ef17-402d-8ece-5b12c1e7220e" xlink:to="loc_flnc_UncommittedLineOfCreditAgreementMember_3be5c8d0-01fe-4ea0-8fd4-d542728e18f5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/DebtPledgedasCollateralDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#DebtPledgedasCollateralDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/DebtPledgedasCollateralDetails" xlink:type="extended" id="if68f6aa81d9f45fdb5757b558bab62f1_DebtPledgedasCollateralDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_FinancingReceivableAfterAllowanceForCreditLossTransferred_db61cf07-6730-438c-b6c7-802eaeb86326" xlink:href="flnc-20221231.xsd#flnc_FinancingReceivableAfterAllowanceForCreditLossTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:to="loc_flnc_FinancingReceivableAfterAllowanceForCreditLossTransferred_db61cf07-6730-438c-b6c7-802eaeb86326" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ProceedsFromBorrowingsAgainstNoteReceivable_9a707014-2093-4dc7-bff7-cda7072e7578" xlink:href="flnc-20221231.xsd#flnc_ProceedsFromBorrowingsAgainstNoteReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:to="loc_flnc_ProceedsFromBorrowingsAgainstNoteReceivable_9a707014-2093-4dc7-bff7-cda7072e7578" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_8c25dafe-5d9c-49c8-a34b-e3e01316bf82" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:to="loc_us-gaap_DebtInstrumentTerm_8c25dafe-5d9c-49c8-a34b-e3e01316bf82" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_7840d817-db01-4b83-901b-1b00ff50e106" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:to="loc_us-gaap_InterestExpenseDebt_7840d817-db01-4b83-901b-1b00ff50e106" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralTable_28b1d9f0-896a-4d0c-a42a-78dbeb58aaba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_622943cb-47c9-4835-a85c-026d97b7724e" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralTable_28b1d9f0-896a-4d0c-a42a-78dbeb58aaba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_6cdfa672-6a4a-4fc5-a775-77bd31a451f4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralTable_28b1d9f0-896a-4d0c-a42a-78dbeb58aaba" xlink:to="loc_srt_StatementScenarioAxis_6cdfa672-6a4a-4fc5-a775-77bd31a451f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_6cdfa672-6a4a-4fc5-a775-77bd31a451f4_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_6cdfa672-6a4a-4fc5-a775-77bd31a451f4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_6cdfa672-6a4a-4fc5-a775-77bd31a451f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_ce8adf40-aff3-422a-bda4-784566b3975e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_6cdfa672-6a4a-4fc5-a775-77bd31a451f4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_ce8adf40-aff3-422a-bda4-784566b3975e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_986e046f-4e8d-44c7-8d3f-1bc2fa5260f3" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_ce8adf40-aff3-422a-bda4-784566b3975e" xlink:to="loc_srt_ScenarioForecastMember_986e046f-4e8d-44c7-8d3f-1bc2fa5260f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1c832e3c-3209-43ce-afd8-a4356fe8b8b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralTable_28b1d9f0-896a-4d0c-a42a-78dbeb58aaba" xlink:to="loc_us-gaap_DebtInstrumentAxis_1c832e3c-3209-43ce-afd8-a4356fe8b8b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1c832e3c-3209-43ce-afd8-a4356fe8b8b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1c832e3c-3209-43ce-afd8-a4356fe8b8b7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1c832e3c-3209-43ce-afd8-a4356fe8b8b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e16dd4ba-c1a9-411a-953c-2e36698ce4e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1c832e3c-3209-43ce-afd8-a4356fe8b8b7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e16dd4ba-c1a9-411a-953c-2e36698ce4e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_BorrowingsAgainstNoteReceivableMember_eadaac69-28c4-46d4-b9bf-9e695af4817a" xlink:href="flnc-20221231.xsd#flnc_BorrowingsAgainstNoteReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e16dd4ba-c1a9-411a-953c-2e36698ce4e7" xlink:to="loc_flnc_BorrowingsAgainstNoteReceivableMember_eadaac69-28c4-46d4-b9bf-9e695af4817a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CommitmentandContingenciesPurchaseCommitmentsDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#CommitmentandContingenciesPurchaseCommitmentsDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CommitmentandContingenciesPurchaseCommitmentsDetails" xlink:type="extended" id="i44834293b9fb4c6f9c17f4589bde427f_CommitmentandContingenciesPurchaseCommitmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d9d70c2d-5f33-474b-a73c-084dd636801d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligationFiscalYearMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d9d70c2d-5f33-474b-a73c-084dd636801d" xlink:to="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_ba51ecaf-dea8-4b71-936e-93f34cccfd42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:to="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_ba51ecaf-dea8-4b71-936e-93f34cccfd42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_b443a16a-d8b4-4d69-8d03-10f675710106" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligationDueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:to="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_b443a16a-d8b4-4d69-8d03-10f675710106" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInSecondYear_1966231e-daf0-4151-9766-0a035b0f9c70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligationDueInSecondYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:to="loc_us-gaap_PurchaseObligationDueInSecondYear_1966231e-daf0-4151-9766-0a035b0f9c70" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_PurchaseObligationToBePaidYearThreeAndThereafter_219e2a7c-b31c-4fb7-adcb-92e2f627061a" xlink:href="flnc-20221231.xsd#flnc_PurchaseObligationToBePaidYearThreeAndThereafter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:to="loc_flnc_PurchaseObligationToBePaidYearThreeAndThereafter_219e2a7c-b31c-4fb7-adcb-92e2f627061a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligation_a9c7240c-2038-4850-b887-e9a3989166d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseObligationFiscalYearMaturityAbstract_de42331a-fe0f-44e1-85ef-cf5a7e0a5d3f" xlink:to="loc_us-gaap_PurchaseObligation_a9c7240c-2038-4850-b887-e9a3989166d2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:href="flnc-20221231.xsd#flnc_LiquidatedDamagesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d9d70c2d-5f33-474b-a73c-084dd636801d" xlink:to="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsFutureMinimumPaymentsRemainderOfFiscalYear_a7d051d9-e163-411e-b039-853823083899" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:to="loc_us-gaap_OtherCommitmentsFutureMinimumPaymentsRemainderOfFiscalYear_a7d051d9-e163-411e-b039-853823083899" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_fc02585f-7859-4523-8f04-8c5799def80f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentDueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:to="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_fc02585f-7859-4523-8f04-8c5799def80f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentDueInSecondYear_eb96a6d6-b9b6-4aba-a02b-62964db78ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentDueInSecondYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:to="loc_us-gaap_OtherCommitmentDueInSecondYear_eb96a6d6-b9b6-4aba-a02b-62964db78ac1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_OtherCommitmentToBePaidYearThreeAndThereafter_7187fbc0-7eb8-490b-bb23-61dec0ac7650" xlink:href="flnc-20221231.xsd#flnc_OtherCommitmentToBePaidYearThreeAndThereafter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:to="loc_flnc_OtherCommitmentToBePaidYearThreeAndThereafter_7187fbc0-7eb8-490b-bb23-61dec0ac7650" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_68708ce0-3af5-4f99-813f-286bf53621c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_flnc_LiquidatedDamagesAbstract_1bc007c1-3598-4fa4-8856-e6a8326dc3b0" xlink:to="loc_us-gaap_OtherCommitment_68708ce0-3af5-4f99-813f-286bf53621c1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_b19fe491-1c20-43c2-a8a9-7850f6fee192" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d9d70c2d-5f33-474b-a73c-084dd636801d" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_b19fe491-1c20-43c2-a8a9-7850f6fee192" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_b19fe491-1c20-43c2-a8a9-7850f6fee192" xlink:to="loc_us-gaap_OtherCommitmentsAxis_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8" xlink:to="loc_us-gaap_OtherCommitmentsDomain_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_05b7291c-c311-4a55-8397-760db6648da8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_5b63f1d6-1f2c-4c2b-b42c-9d45276c2da8" xlink:to="loc_us-gaap_OtherCommitmentsDomain_05b7291c-c311-4a55-8397-760db6648da8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LiquidatedDamagesMember_db12ee30-ca23-46b2-ac4a-5f573f8a97ba" xlink:href="flnc-20221231.xsd#flnc_LiquidatedDamagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_05b7291c-c311-4a55-8397-760db6648da8" xlink:to="loc_flnc_LiquidatedDamagesMember_db12ee30-ca23-46b2-ac4a-5f573f8a97ba" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/CommitmentandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#CommitmentandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/CommitmentandContingenciesNarrativeDetails" xlink:type="extended" id="i6c40284fc2364b449aeda02147da5062_CommitmentandContingenciesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_PaymentsForAdvancesOnInventoryPurchases_ba5ef59d-910b-471e-a8d3-03bc3490b979" xlink:href="flnc-20221231.xsd#flnc_PaymentsForAdvancesOnInventoryPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_flnc_PaymentsForAdvancesOnInventoryPurchases_ba5ef59d-910b-471e-a8d3-03bc3490b979" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvancesOnInventoryPurchases_310bdf09-5d3a-4ebb-832c-262efc3ab0c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdvancesOnInventoryPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_AdvancesOnInventoryPurchases_310bdf09-5d3a-4ebb-832c-262efc3ab0c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CostsOfGoodsAndServicesReductionFromClaimSettlement_eb07b22b-15f8-467b-aa18-3e2d7f9c12c2" xlink:href="flnc-20221231.xsd#flnc_CostsOfGoodsAndServicesReductionFromClaimSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_flnc_CostsOfGoodsAndServicesReductionFromClaimSettlement_eb07b22b-15f8-467b-aa18-3e2d7f9c12c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyAccrual_78628de8-c42e-4dc2-977b-110025066739" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductWarrantyAccrual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_ProductWarrantyAccrual_78628de8-c42e-4dc2-977b-110025066739" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_LimitedWarrantyPeriod_8854e9d5-0feb-4309-baaf-9a289c9b5069" xlink:href="flnc-20221231.xsd#flnc_LimitedWarrantyPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_flnc_LimitedWarrantyPeriod_8854e9d5-0feb-4309-baaf-9a289c9b5069" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryValuationReserves_e19efdda-2056-47c0-b4df-d26d13efbccc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryValuationReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_InventoryValuationReserves_e19efdda-2056-47c0-b4df-d26d13efbccc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_InventoryValuationReservesInventoryWriteDown_e06ab4e3-97c8-4c6b-883c-2b681e2a47a2" xlink:href="flnc-20221231.xsd#flnc_InventoryValuationReservesInventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_flnc_InventoryValuationReservesInventoryWriteDown_e06ab4e3-97c8-4c6b-883c-2b681e2a47a2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InsuranceSettlementsReceivable_9ec4c7da-bbdf-4892-822a-e1e05d861bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InsuranceSettlementsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_InsuranceSettlementsReceivable_9ec4c7da-bbdf-4892-822a-e1e05d861bf3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromInsuranceSettlementOperatingActivities_a86678ca-0087-4a10-8528-ffd6c19e1c2c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromInsuranceSettlementOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_ProceedsFromInsuranceSettlementOperatingActivities_a86678ca-0087-4a10-8528-ffd6c19e1c2c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_bbe0a47a-411f-4558-b62d-7188c9ac9f75" xlink:to="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_74faaf09-b86b-4b46-b341-dc2b3b994425" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:to="loc_srt_LitigationCaseAxis_74faaf09-b86b-4b46-b341-dc2b3b994425" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_74faaf09-b86b-4b46-b341-dc2b3b994425_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_74faaf09-b86b-4b46-b341-dc2b3b994425" xlink:to="loc_srt_LitigationCaseTypeDomain_74faaf09-b86b-4b46-b341-dc2b3b994425_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_ecc1cb42-1d64-4f85-a1fb-9bfbc8eeb03e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_74faaf09-b86b-4b46-b341-dc2b3b994425" xlink:to="loc_srt_LitigationCaseTypeDomain_ecc1cb42-1d64-4f85-a1fb-9bfbc8eeb03e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_A2021CargoLossIncidentMember_8e6d2387-db14-4436-827f-e9268fb96620" xlink:href="flnc-20221231.xsd#flnc_A2021CargoLossIncidentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_ecc1cb42-1d64-4f85-a1fb-9bfbc8eeb03e" xlink:to="loc_flnc_A2021CargoLossIncidentMember_8e6d2387-db14-4436-827f-e9268fb96620" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_19b2553c-abbc-41d7-90fb-d90740302cb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_19b2553c-abbc-41d7-90fb-d90740302cb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_19b2553c-abbc-41d7-90fb-d90740302cb6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_19b2553c-abbc-41d7-90fb-d90740302cb6" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_19b2553c-abbc-41d7-90fb-d90740302cb6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_e0011746-3929-4120-bc5d-4b60e70844c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_19b2553c-abbc-41d7-90fb-d90740302cb6" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_e0011746-3929-4120-bc5d-4b60e70844c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_InventoryCapacityGuaranteeMember_fbddc167-ebe6-4871-8a3b-2e00de372b8b" xlink:href="flnc-20221231.xsd#flnc_InventoryCapacityGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_e0011746-3929-4120-bc5d-4b60e70844c2" xlink:to="loc_flnc_InventoryCapacityGuaranteeMember_fbddc167-ebe6-4871-8a3b-2e00de372b8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_f8d7acc2-a17b-416e-8b49-87f31e4557bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5e32bdc0-aa92-4bb8-ac9b-d39e9c3ee3a9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_f8d7acc2-a17b-416e-8b49-87f31e4557bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_5f64538d-502b-4174-ae96-7aede6795756" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f8d7acc2-a17b-416e-8b49-87f31e4557bf" xlink:to="loc_us-gaap_CostOfSalesMember_5f64538d-502b-4174-ae96-7aede6795756" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_58577676-32e2-4e25-a085-ec44775d3995" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_52dfacec-224b-4235-802f-2e52b5b14787" xlink:to="loc_srt_RangeAxis_58577676-32e2-4e25-a085-ec44775d3995" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_58577676-32e2-4e25-a085-ec44775d3995_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_58577676-32e2-4e25-a085-ec44775d3995" xlink:to="loc_srt_RangeMember_58577676-32e2-4e25-a085-ec44775d3995_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c2e14601-23da-4734-83aa-52516eb8f2e8" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_58577676-32e2-4e25-a085-ec44775d3995" xlink:to="loc_srt_RangeMember_c2e14601-23da-4734-83aa-52516eb8f2e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_972aa944-c9a7-4b4f-a9aa-354b9afd99f6" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c2e14601-23da-4734-83aa-52516eb8f2e8" xlink:to="loc_srt_MinimumMember_972aa944-c9a7-4b4f-a9aa-354b9afd99f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_9c39104d-c399-4679-98ab-5563b3be4a86" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c2e14601-23da-4734-83aa-52516eb8f2e8" xlink:to="loc_srt_MaximumMember_9c39104d-c399-4679-98ab-5563b3be4a86" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RelatedPartyTransactionsAdditionalInformationDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RelatedPartyTransactionsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RelatedPartyTransactionsAdditionalInformationDetails" xlink:type="extended" id="ibddada30706e4a6ea58fe9652199c44f_RelatedPartyTransactionsAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedBalanceShares_e066f8f2-4c2f-43c2-ba45-8dfc280d5832" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentOwnedBalanceShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_us-gaap_InvestmentOwnedBalanceShares_e066f8f2-4c2f-43c2-ba45-8dfc280d5832" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_42322d49-75bf-4554-a3d4-2fbb56308844" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_42322d49-75bf-4554-a3d4-2fbb56308844" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_b659adc0-9c8d-4df2-a3ef-c75f6223014d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_b659adc0-9c8d-4df2-a3ef-c75f6223014d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromRelatedParties_acc0514d-de85-4f30-9ff1-d0c1f3a2284f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_us-gaap_RevenueFromRelatedParties_acc0514d-de85-4f30-9ff1-d0c1f3a2284f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ReceivablesRelatedPartiesAllowanceForCreditLoss_e4359e2c-d006-43c8-9240-c69bf0fbdda7" xlink:href="flnc-20221231.xsd#flnc_ReceivablesRelatedPartiesAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_flnc_ReceivablesRelatedPartiesAllowanceForCreditLoss_e4359e2c-d006-43c8-9240-c69bf0fbdda7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_9ebcea57-0d31-4d9e-b53b-06ca6290f7d8" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09" xlink:to="loc_us-gaap_RelatedPartyDomain_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_73be047d-1d7c-4a28-aa80-98b8e8acec23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0ff2b7c0-dfa2-4fbd-ab09-9416a6de4e09" xlink:to="loc_us-gaap_RelatedPartyDomain_73be047d-1d7c-4a28-aa80-98b8e8acec23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_bc29c733-c2e5-4487-bb27-683e7364506b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_73be047d-1d7c-4a28-aa80-98b8e8acec23" xlink:to="loc_srt_AffiliatedEntityMember_bc29c733-c2e5-4487-bb27-683e7364506b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:to="loc_srt_CounterpartyNameAxis_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_724c2c39-7089-4cfb-86d3-e460bd4f4d2c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_fa4c0bfb-6bc3-46d9-b1d6-6bbb53e00342" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_724c2c39-7089-4cfb-86d3-e460bd4f4d2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_AESGridStabilityLLCMember_56b1f495-5a13-4c22-9104-db5fd59d8d07" xlink:href="flnc-20221231.xsd#flnc_AESGridStabilityLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_724c2c39-7089-4cfb-86d3-e460bd4f4d2c" xlink:to="loc_flnc_AESGridStabilityLLCMember_56b1f495-5a13-4c22-9104-db5fd59d8d07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_SiemensIndustryIncMember_c01f1786-cf26-40c2-aa0d-e1efeaa504ca" xlink:href="flnc-20221231.xsd#flnc_SiemensIndustryIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_724c2c39-7089-4cfb-86d3-e460bd4f4d2c" xlink:to="loc_flnc_SiemensIndustryIncMember_c01f1786-cf26-40c2-aa0d-e1efeaa504ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_142951de-9a63-4267-9c04-77886e02e251" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:to="loc_us-gaap_StatementClassOfStockAxis_142951de-9a63-4267-9c04-77886e02e251" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_142951de-9a63-4267-9c04-77886e02e251_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_142951de-9a63-4267-9c04-77886e02e251" xlink:to="loc_us-gaap_ClassOfStockDomain_142951de-9a63-4267-9c04-77886e02e251_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_578ff5e6-48a2-481c-b411-880243265168" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_142951de-9a63-4267-9c04-77886e02e251" xlink:to="loc_us-gaap_ClassOfStockDomain_578ff5e6-48a2-481c-b411-880243265168" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_CommonClassB1Member_06eb0337-37b1-41e0-896f-4d295ee33e6f" xlink:href="flnc-20221231.xsd#flnc_CommonClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_578ff5e6-48a2-481c-b411-880243265168" xlink:to="loc_flnc_CommonClassB1Member_06eb0337-37b1-41e0-896f-4d295ee33e6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_f48bfc57-8e0b-49a1-8e03-131696a13a07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_578ff5e6-48a2-481c-b411-880243265168" xlink:to="loc_us-gaap_CommonClassAMember_f48bfc57-8e0b-49a1-8e03-131696a13a07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_06e0c65e-fa72-44f6-9499-81d86be77aa1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97e67720-2652-4b5e-9165-2ee2ed30903f" xlink:to="loc_srt_OwnershipAxis_06e0c65e-fa72-44f6-9499-81d86be77aa1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_06e0c65e-fa72-44f6-9499-81d86be77aa1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_06e0c65e-fa72-44f6-9499-81d86be77aa1" xlink:to="loc_srt_OwnershipDomain_06e0c65e-fa72-44f6-9499-81d86be77aa1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_4867d1ea-c842-4442-b976-e1ff19152848" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_06e0c65e-fa72-44f6-9499-81d86be77aa1" xlink:to="loc_srt_OwnershipDomain_4867d1ea-c842-4442-b976-e1ff19152848" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_FluenceEnergyINCMember_7e6b7d52-48d6-495a-8a4b-30a19f387bab" xlink:href="flnc-20221231.xsd#flnc_FluenceEnergyINCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_4867d1ea-c842-4442-b976-e1ff19152848" xlink:to="loc_flnc_FluenceEnergyINCMember_7e6b7d52-48d6-495a-8a4b-30a19f387bab" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/StockBasedCompensationAdditionalInformationDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#StockBasedCompensationAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/StockBasedCompensationAdditionalInformationDetails" xlink:type="extended" id="icd183f98b9334efcb0349c2be1e34087_StockBasedCompensationAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_2103f1a7-1ab3-4f34-a381-67e8a217989e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_2103f1a7-1ab3-4f34-a381-67e8a217989e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_254d2225-8854-4140-a4eb-72fcf8de679e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_254d2225-8854-4140-a4eb-72fcf8de679e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_6a2941c2-a01f-4d63-b771-6dc3290d0704" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_6a2941c2-a01f-4d63-b771-6dc3290d0704" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_e0b6b692-15e1-42f3-b5ee-e36c9dac503d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_e0b6b692-15e1-42f3-b5ee-e36c9dac503d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_16d76393-5a60-4a0b-a7fb-09107a930701" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_16d76393-5a60-4a0b-a7fb-09107a930701" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_e9935406-69a6-4ab1-ac14-64dfb48db4b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_e9935406-69a6-4ab1-ac14-64dfb48db4b6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_d7a8bc4a-1e78-4d7e-bf89-c7295e3a4e26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_d7a8bc4a-1e78-4d7e-bf89-c7295e3a4e26" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_b24ff851-bf88-481a-92c0-779fd76d9785" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_b24ff851-bf88-481a-92c0-779fd76d9785" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_17e3ac84-1992-4833-8441-daf06d706a32" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_17e3ac84-1992-4833-8441-daf06d706a32" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_41dbbac0-f241-48e9-9897-9b4196cb3597" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_41dbbac0-f241-48e9-9897-9b4196cb3597" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_d119a281-9dd4-4381-b75f-7c13ce45ce7e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_d119a281-9dd4-4381-b75f-7c13ce45ce7e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_52b6e0dc-f375-4767-a33d-ce251bcf7d07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_52b6e0dc-f375-4767-a33d-ce251bcf7d07" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3dc27097-196b-4429-ad2a-0453c1e6f2a6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_a4d76a6f-187c-4be1-ad07-b4d09c993780" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:to="loc_us-gaap_AwardTypeAxis_a4d76a6f-187c-4be1-ad07-b4d09c993780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a4d76a6f-187c-4be1-ad07-b4d09c993780_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_a4d76a6f-187c-4be1-ad07-b4d09c993780" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a4d76a6f-187c-4be1-ad07-b4d09c993780_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1b599db7-0db3-4375-a30e-18eafdd9f002" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_a4d76a6f-187c-4be1-ad07-b4d09c993780" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1b599db7-0db3-4375-a30e-18eafdd9f002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_cfa3c480-0a69-43a3-b48a-3637a9c87f07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1b599db7-0db3-4375-a30e-18eafdd9f002" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_cfa3c480-0a69-43a3-b48a-3637a9c87f07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_cde26485-9550-4bcc-9d1f-cbdca7d314cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1b599db7-0db3-4375-a30e-18eafdd9f002" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_cde26485-9550-4bcc-9d1f-cbdca7d314cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_fe042b67-1f52-4780-b8d0-ee1cce35ce98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1b599db7-0db3-4375-a30e-18eafdd9f002" xlink:to="loc_us-gaap_EmployeeStockOptionMember_fe042b67-1f52-4780-b8d0-ee1cce35ce98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_c6882c19-269d-4c48-9c76-33b90f0335ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:to="loc_us-gaap_PlanNameAxis_c6882c19-269d-4c48-9c76-33b90f0335ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_c6882c19-269d-4c48-9c76-33b90f0335ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_c6882c19-269d-4c48-9c76-33b90f0335ca" xlink:to="loc_us-gaap_PlanNameDomain_c6882c19-269d-4c48-9c76-33b90f0335ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_e1e0bb31-64c5-44c9-ab4e-211348b97f97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_c6882c19-269d-4c48-9c76-33b90f0335ca" xlink:to="loc_us-gaap_PlanNameDomain_e1e0bb31-64c5-44c9-ab4e-211348b97f97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_TheOptionPlanMember_4818de58-f52d-4900-a478-a64c7f0f73f5" xlink:href="flnc-20221231.xsd#flnc_TheOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_e1e0bb31-64c5-44c9-ab4e-211348b97f97" xlink:to="loc_flnc_TheOptionPlanMember_4818de58-f52d-4900-a478-a64c7f0f73f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_A2021PlanMember_95c80d26-573e-4205-bb59-41ed4138fd4e" xlink:href="flnc-20221231.xsd#flnc_A2021PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_e1e0bb31-64c5-44c9-ab4e-211348b97f97" xlink:to="loc_flnc_A2021PlanMember_95c80d26-573e-4205-bb59-41ed4138fd4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_ac50787a-7d8a-410e-b7de-cb40c50c084b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:to="loc_srt_TitleOfIndividualAxis_ac50787a-7d8a-410e-b7de-cb40c50c084b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ac50787a-7d8a-410e-b7de-cb40c50c084b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_ac50787a-7d8a-410e-b7de-cb40c50c084b" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ac50787a-7d8a-410e-b7de-cb40c50c084b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ebcd9c75-52f1-47a5-ab3a-50106e3d197a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_ac50787a-7d8a-410e-b7de-cb40c50c084b" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ebcd9c75-52f1-47a5-ab3a-50106e3d197a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveOfficerMember_b429a8e6-d86b-44f6-8fbe-566e74d800ae" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ebcd9c75-52f1-47a5-ab3a-50106e3d197a" xlink:to="loc_srt_ExecutiveOfficerMember_b429a8e6-d86b-44f6-8fbe-566e74d800ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_c3362614-2877-47d3-b34d-02d53736fd54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2c31be50-62c4-49dd-ae61-be26ee341a56" xlink:to="loc_us-gaap_VestingAxis_c3362614-2877-47d3-b34d-02d53736fd54" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_c3362614-2877-47d3-b34d-02d53736fd54_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_c3362614-2877-47d3-b34d-02d53736fd54" xlink:to="loc_us-gaap_VestingDomain_c3362614-2877-47d3-b34d-02d53736fd54_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_0ccdfb1e-22b4-467d-b069-57801134322e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_c3362614-2877-47d3-b34d-02d53736fd54" xlink:to="loc_us-gaap_VestingDomain_0ccdfb1e-22b4-467d-b069-57801134322e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_604b95e8-2f62-4e60-979d-02f59f503614" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_0ccdfb1e-22b4-467d-b069-57801134322e" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_604b95e8-2f62-4e60-979d-02f59f503614" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_27fa7e9e-f74b-4cdf-9bb4-d6f1014a1446" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_0ccdfb1e-22b4-467d-b069-57801134322e" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_27fa7e9e-f74b-4cdf-9bb4-d6f1014a1446" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_50d6bec1-91cc-4a18-b08f-9633fec480e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_0ccdfb1e-22b4-467d-b069-57801134322e" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_50d6bec1-91cc-4a18-b08f-9633fec480e5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/StockBasedCompensationStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#StockBasedCompensationStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/StockBasedCompensationStockBasedCompensationExpenseDetails" xlink:type="extended" id="i6e338ccdfb5f4b16b072519d0ff81c3b_StockBasedCompensationStockBasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2c482c1a-7856-4593-b672-a83838cdc59c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_135e6158-431c-48c8-b705-ada8f15efc79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2c482c1a-7856-4593-b672-a83838cdc59c" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_135e6158-431c-48c8-b705-ada8f15efc79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8365dcf1-3c33-4261-b625-59c47b02f702" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2c482c1a-7856-4593-b672-a83838cdc59c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8365dcf1-3c33-4261-b625-59c47b02f702" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_baaecda4-bb91-4d0f-ba64-38cb77301086" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8365dcf1-3c33-4261-b625-59c47b02f702" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_baaecda4-bb91-4d0f-ba64-38cb77301086" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_baaecda4-bb91-4d0f-ba64-38cb77301086_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_baaecda4-bb91-4d0f-ba64-38cb77301086" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_baaecda4-bb91-4d0f-ba64-38cb77301086_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_baaecda4-bb91-4d0f-ba64-38cb77301086" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_9baa0ef0-d70b-4be3-8b4f-09baeec7250b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:to="loc_us-gaap_CostOfSalesMember_9baa0ef0-d70b-4be3-8b4f-09baeec7250b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_62931bbf-71b6-4dac-b2f6-0dc6642e5c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_62931bbf-71b6-4dac-b2f6-0dc6642e5c9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_dfd96fc9-bcb1-44ef-96dc-6d8b13ca2ec2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_dfd96fc9-bcb1-44ef-96dc-6d8b13ca2ec2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_cef62834-1587-4654-8240-eb7e101691a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4fdf9422-af5a-4305-9317-cf16229a2bf4" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_cef62834-1587-4654-8240-eb7e101691a0" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/RestructuringPlanDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#RestructuringPlanDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/RestructuringPlanDetails" xlink:type="extended" id="ic01c01525adc4882815b74ebf3efa6e1_RestructuringPlanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_e0de5af7-a949-4454-9aab-744bfb5aae29" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_471b1ac5-ebb0-4c38-8a8c-1d3f1c8de333" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestructuringAndRelatedCostCostIncurredToDate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_e0de5af7-a949-4454-9aab-744bfb5aae29" xlink:to="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_471b1ac5-ebb0-4c38-8a8c-1d3f1c8de333" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_07a96c39-cda0-4f16-9138-8ce119696971" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_e0de5af7-a949-4454-9aab-744bfb5aae29" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_07a96c39-cda0-4f16-9138-8ce119696971" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_6afccf8d-b750-413b-b968-25df92a63290" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_07a96c39-cda0-4f16-9138-8ce119696971" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_6afccf8d-b750-413b-b968-25df92a63290" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_6afccf8d-b750-413b-b968-25df92a63290_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_6afccf8d-b750-413b-b968-25df92a63290" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_6afccf8d-b750-413b-b968-25df92a63290_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_78a07d18-c45d-4d54-aa2b-bf939feabfd1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_6afccf8d-b750-413b-b968-25df92a63290" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_78a07d18-c45d-4d54-aa2b-bf939feabfd1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_7d6a5abd-ab77-47af-8a44-2b0c213cdd3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_78a07d18-c45d-4d54-aa2b-bf939feabfd1" xlink:to="loc_us-gaap_EmployeeSeveranceMember_7d6a5abd-ab77-47af-8a44-2b0c213cdd3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_ConsultingMember_d08bda37-293e-4d3e-ab9e-06efd8193a09" xlink:href="flnc-20221231.xsd#flnc_ConsultingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_78a07d18-c45d-4d54-aa2b-bf939feabfd1" xlink:to="loc_flnc_ConsultingMember_d08bda37-293e-4d3e-ab9e-06efd8193a09" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fluenceenergy.com/role/InvestmentinJointVentureDetails" xlink:type="simple" xlink:href="flnc-20221231.xsd#InvestmentinJointVentureDetails"/>
  <link:definitionLink xlink:role="http://fluenceenergy.com/role/InvestmentinJointVentureDetails" xlink:type="extended" id="i8f095100e97c4ee89d74733c4412425d_InvestmentinJointVentureDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_892496c8-a22b-43b5-8360-bbb36502ee0f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInterestInJointVenture_cc1bd8fa-476e-47d2-a558-4e4770d7fe94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireInterestInJointVenture"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_892496c8-a22b-43b5-8360-bbb36502ee0f" xlink:to="loc_us-gaap_PaymentsToAcquireInterestInJointVenture_cc1bd8fa-476e-47d2-a558-4e4770d7fe94" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_9ab134d2-b31d-4c94-a747-d55934a10ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_892496c8-a22b-43b5-8360-bbb36502ee0f" xlink:to="loc_us-gaap_LineOfCredit_9ab134d2-b31d-4c94-a747-d55934a10ab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_44f91957-d457-4d69-8146-62d5282615c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_892496c8-a22b-43b5-8360-bbb36502ee0f" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_44f91957-d457-4d69-8146-62d5282615c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_81e2f16d-3c4a-4366-9188-68b2de7c5d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_892496c8-a22b-43b5-8360-bbb36502ee0f" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_81e2f16d-3c4a-4366-9188-68b2de7c5d8d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1b83deab-3573-4ab5-92d3-48a7fc428784" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_81e2f16d-3c4a-4366-9188-68b2de7c5d8d" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1b83deab-3573-4ab5-92d3-48a7fc428784" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_1b83deab-3573-4ab5-92d3-48a7fc428784_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1b83deab-3573-4ab5-92d3-48a7fc428784" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_1b83deab-3573-4ab5-92d3-48a7fc428784_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_402afc8a-1708-4c0d-8e85-ee7552428635" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1b83deab-3573-4ab5-92d3-48a7fc428784" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_402afc8a-1708-4c0d-8e85-ee7552428635" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_flnc_IndiaPartnershipMember_b3cc9ae0-e287-470e-aaff-1dad18abe910" xlink:href="flnc-20221231.xsd#flnc_IndiaPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_402afc8a-1708-4c0d-8e85-ee7552428635" xlink:to="loc_flnc_IndiaPartnershipMember_b3cc9ae0-e287-470e-aaff-1dad18abe910" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
