<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-05-04</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001584207</issuerCik>
        <issuerName>Springleaf Holdings, Inc.</issuerName>
        <issuerTradingSymbol>LEAF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000005272</rptOwnerCik>
            <rptOwnerName>AMERICAN INTERNATIONAL GROUP INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>175 WATER STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10038</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001417296</rptOwnerCik>
            <rptOwnerName>AIG Capital CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AMERICAN INTERNATIONAL GROUP, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>175 WATER STREET</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10038</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2015-05-04</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8447049</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.3413</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4179678</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Springleaf Financial Holdings, LLC</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares of Springleaf Holdings, Inc. common stock are held directly by Springleaf Financial Holdings, LLC. AIG Capital Corporation has the indirect right to vote and in certain circumstances to cause the disposition of these shares. AIG Capital Corporation is wholly owned by American International Group, Inc. Each reporting person disclaims beneficial ownership of all reported shares except to the extent of its pecuniary interest therein and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for the purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.</footnote>
    </footnotes>

    <remarks>Exhibit 99.1 Joint Filer Information incorporated herein by reference. As of May 4, 2015, following the transactions reported herein, the reporting persons ceased to be a beneficial owner of 10% or more of the Common Stock of Springleaf Holdings, Inc.</remarks>

    <ownerSignature>
        <signatureName>AIG Capital Corporation, By: /s/ Ed Holmes, General Counsel and Secretary</signatureName>
        <signatureDate>2015-05-06</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>American International Group, Inc. By: /s/ Brian T. Schreiber, Executive Vice President and Deputy Chief Investment Officer</signatureName>
        <signatureDate>2015-05-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
