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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a09080-3c4d-7f9b-8fb0-114a5f92422e,g:64452ef3-e8ec-4b56-afe2-8d01f932df1f-->
<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://eosenergystorage.com/role/Cover" xlink:type="simple" xlink:href="eose-20260910.xsd#Cover"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_01a09080-3c4d-7d49-a938-a5768876650b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_DocumentInformationTable_01a09080-3c4d-7d49-a938-a5768876650b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a09080-3c4d-7e58-a20f-48087071133a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_01a09080-3c4d-7d49-a938-a5768876650b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a09080-3c4d-7e58-a20f-48087071133a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7e58-a20f-48087071133a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a09080-3c4d-7e58-a20f-48087071133a" xlink:to="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7e58-a20f-48087071133a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7311-a4f5-abd03af0fd0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a09080-3c4d-7e58-a20f-48087071133a" xlink:to="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7311-a4f5-abd03af0fd0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_01a09080-3c4d-7b15-b8ca-21479b56669f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7311-a4f5-abd03af0fd0f" xlink:to="loc_us-gaap_CommonStockMember_01a09080-3c4d-7b15-b8ca-21479b56669f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_01a09080-3c4d-759a-9dab-a8848005ce08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a09080-3c4d-7311-a4f5-abd03af0fd0f" xlink:to="loc_us-gaap_WarrantMember_01a09080-3c4d-759a-9dab-a8848005ce08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_01a09080-3c4d-7422-92d9-e8ea09eb3f2a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityRegistrantName_01a09080-3c4d-7422-92d9-e8ea09eb3f2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_01a09080-3c4d-7677-8304-6bfc4c720c33" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityCentralIndexKey_01a09080-3c4d-7677-8304-6bfc4c720c33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_01a09080-3c4d-7664-9bed-08d4d4a43f82" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_AmendmentFlag_01a09080-3c4d-7664-9bed-08d4d4a43f82" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_01a09080-3c4d-778b-b0ab-380e7abbf709" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityEmergingGrowthCompany_01a09080-3c4d-778b-b0ab-380e7abbf709" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_01a09080-3c4d-749c-b5ea-c284aba6e779" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_Security12bTitle_01a09080-3c4d-749c-b5ea-c284aba6e779" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_01a09080-3c4d-76b4-b218-7dca9189fd1f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_TradingSymbol_01a09080-3c4d-76b4-b218-7dca9189fd1f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_01a09080-3c4d-7a11-a571-8e0b269d3522" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_SecurityExchangeName_01a09080-3c4d-7a11-a571-8e0b269d3522" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_01a09080-3c4d-771e-a9f2-99774f2b847e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityFileNumber_01a09080-3c4d-771e-a9f2-99774f2b847e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_01a09080-3c4d-7769-af97-d073f2c8ba69" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityTaxIdentificationNumber_01a09080-3c4d-7769-af97-d073f2c8ba69" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_01a09080-3c4d-7206-a75f-d85bbef63670" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityIncorporationStateCountryCode_01a09080-3c4d-7206-a75f-d85bbef63670" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_01a09080-3c4d-7049-92f0-37422f31dbf1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressAddressLine1_01a09080-3c4d-7049-92f0-37422f31dbf1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_01a09080-3c4d-7da7-b1fe-5e6c129a3f28" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressAddressLine2_01a09080-3c4d-7da7-b1fe-5e6c129a3f28" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine3_01a09080-3c4d-7cf0-a1dd-9028abd9dbad" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressAddressLine3_01a09080-3c4d-7cf0-a1dd-9028abd9dbad" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_01a09080-3c4d-71fd-a179-db64ba298c4f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressCityOrTown_01a09080-3c4d-71fd-a179-db64ba298c4f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_01a09080-3c4d-72f7-a5fe-b169c93a9768" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressStateOrProvince_01a09080-3c4d-72f7-a5fe-b169c93a9768" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_01a09080-3c4d-799f-b41c-fc7f8921e8cd" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_EntityAddressPostalZipCode_01a09080-3c4d-799f-b41c-fc7f8921e8cd" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_01a09080-3c4d-791d-b325-149fd28fec82" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_CityAreaCode_01a09080-3c4d-791d-b325-149fd28fec82" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_01a09080-3c4d-7c97-aaf8-344845d370c0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_LocalPhoneNumber_01a09080-3c4d-7c97-aaf8-344845d370c0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_01a09080-3c4d-79e9-a3d8-c503d81832d1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_WrittenCommunications_01a09080-3c4d-79e9-a3d8-c503d81832d1" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_01a09080-3c4d-7815-a34d-fe8c1ebe9244" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_SolicitingMaterial_01a09080-3c4d-7815-a34d-fe8c1ebe9244" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_01a09080-3c4d-718f-9f78-00fa2cea275a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_PreCommencementTenderOffer_01a09080-3c4d-718f-9f78-00fa2cea275a" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_01a09080-3c4d-7551-b69f-4ab249d9a57f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a09080-3c4d-7c8f-bfae-627071cc3a06" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_01a09080-3c4d-7551-b69f-4ab249d9a57f" xlink:type="arc" order="21"/>
  </link:definitionLink>
</link:linkbase>
