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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-06-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001351541</issuerCik>
        <issuerName>Delek US Holdings, Inc.</issuerName>
        <issuerTradingSymbol>DK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361020</rptOwnerCik>
            <rptOwnerName>Delek Hungary Holding LTD Liability CO</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7, GIBOREI ISRAEL STREET, P.O.B. 8464</rptOwnerStreet1>
            <rptOwnerStreet2>INDUSTRIAL ZONE SOUTH</rptOwnerStreet2>
            <rptOwnerCity>NETANYA</rptOwnerCity>
            <rptOwnerState>L3</rptOwnerState>
            <rptOwnerZipCode>42504</rptOwnerZipCode>
            <rptOwnerStateDescription>ISRAEL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361371</rptOwnerCik>
            <rptOwnerName>Delek Group, Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7, GIBOREI ISRAEL STREET, P.O.B. 8464</rptOwnerStreet1>
            <rptOwnerStreet2>INDUSTRIAL ZONE SOUTH</rptOwnerStreet2>
            <rptOwnerCity>NETANYA</rptOwnerCity>
            <rptOwnerState>L3</rptOwnerState>
            <rptOwnerZipCode>42504</rptOwnerZipCode>
            <rptOwnerStateDescription>ISRAEL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361291</rptOwnerCik>
            <rptOwnerName>Delek Petroleum, Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7, GIBOREI ISRAEL STREET, P.O.B. 8464</rptOwnerStreet1>
            <rptOwnerStreet2>INDUSTRIAL ZONE SOUTH</rptOwnerStreet2>
            <rptOwnerCity>NETANYA</rptOwnerCity>
            <rptOwnerState>L3</rptOwnerState>
            <rptOwnerZipCode>42504</rptOwnerZipCode>
            <rptOwnerStateDescription>ISRAEL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361468</rptOwnerCik>
            <rptOwnerName>Sharon Itshak</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7, GIBOREI ISRAEL STREET</rptOwnerStreet1>
            <rptOwnerStreet2>P.O.B. 8464, INDUSTRIAL ZONE SOUTH</rptOwnerStreet2>
            <rptOwnerCity>NETANYA</rptOwnerCity>
            <rptOwnerState>L3</rptOwnerState>
            <rptOwnerZipCode>42504</rptOwnerZipCode>
            <rptOwnerStateDescription>ISRAEL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-06-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2000000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>32.18</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19536432</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This Form 4 is filed jointly by Delek Hungary Holding Limited Liability Company (&quot;Delek Hungary&quot;), Delek Petroleum, Ltd. (&quot;Delek Petroleum&quot;), Delek Group, Ltd. (&quot;Delek Group&quot;) and Itshak Sharon.  On June 13, 2013, Delek Hungary sold 2,000,000 shares of Common Stock of Delek US Holdings, Inc. in a block trade.</footnote>
        <footnote id="F2">Represents shares directly owned by Delek Hungary.  Delek Hungary is a subsidiary of Delek Petroleum and Delek Group.  Mr. Sharon has voting and investment control over Delek Group, the parent company of Delek Petroleum and Delek Hungary, through corporations that he controls.  Delek Petroleum, Delek Group and Mr. Sharon disclaim beneficial ownership of these shares except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Leora Pratt Levin, Attorney-In-Fact</signatureName>
        <signatureDate>2013-06-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
