<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-05-14</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000055067</issuerCik>
        <issuerName>KELLOGG CO</issuerName>
        <issuerTradingSymbol>K</issuerTradingSymbol></issuer>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0001197921</rptOwnerCik>
            <rptOwnerName>KELLOGG W K FOUNDATION TRUST</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>1</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText></reportingOwnerRelationship></reportingOwner>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0001197916</rptOwnerCik>
            <rptOwnerName>KELLOGG W K FOUNDATION</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>1</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText></reportingOwnerRelationship></reportingOwner>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>2003-05-14</value></transactionDate>
<deemedExecutionDate>
<value>2003-05-14</value></deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>25000</value></transactionShares>
<transactionValue>
<value>33.5053</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>D</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>125839940</value>
<footnoteId id="F1"/>
<footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
<footnoteId id="F1"/></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<footnotes>
<footnote id="F1">125,839,940 shares are directly owned by the W.K. Kellogg Foundation Trust (the &quot;Trust&quot;) of which Jonathan T. Walton, William C. Richardson, Carlos M. Gutierrez, and The Bank of New York are Trustees and the W.K. Kellogg Foundation (the &quot;Foundation&quot;) is the sole beneficiary.</footnote>
<footnote id="F2">721,920 shares are indirectly owned by the Carrie Staines Kellogg Trust # 5977 of which the Foundation is currently a beneficiary.</footnote></footnotes>
<ownerSignature>
<signatureName>Catherine P. Boyle, Vice President, The Bank of New York as CorporateTrustee</signatureName>
<signatureDate>2003-05-22</signatureDate></ownerSignature></ownershipDocument>


