<SUBMISSION>
<ACCESSION-NUMBER>0000945094-04-000776
<TYPE>4/A
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20041220
<FILING-DATE>20041222
<DATE-OF-FILING-DATE-CHANGE>20041222
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>ALLSTATE CORP
<CIK>0000899051
<ASSIGNED-SIC>6331
<IRS-NUMBER>363871531
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>2775 SANDERS ROAD
<CITY>NORTHBROOK
<STATE>IL
<ZIP>60062
<PHONE>8474025000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>2775 SANDERS ROAD
<CITY>NORTHBROOK
<STATE>IL
<ZIP>60062
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>MCCABE MICHAEL J
<CIK>0001199798
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4/A
<ACT>34
<FILE-NUMBER>001-11840
<FILM-NUMBER>041221062
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>2775 SANDERS RD
<CITY>NORTHBROOK
<STATE>IL
<ZIP>60062
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>c0001199798d20041222f4af.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2004-12-20</periodOfReport>

    <dateOfOriginalSubmission>2004-12-22</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000899051</issuerCik>
        <issuerName>ALLSTATE CORP</issuerName>
        <issuerTradingSymbol>ALL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001199798</rptOwnerCik>
            <rptOwnerName>MCCABE MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THE ALLSTATE CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>2775 SANDERS ROAD</rptOwnerStreet2>
            <rptOwnerCity>NORTHBROOK</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60062-6127</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>V.P. and General Counsel</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-12-20</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>26753</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.3219</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>48650</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by Son</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2255.325</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by 401(k) Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1(c) trading plan adopted by the reporting person on December 3, 2004.</footnote>
        <footnote id="F2">Reflects acquisition of 34.835 shares of The Allstate Corporation common stock since May 12, 2004 under The Savings and Profit Sharing Fund of Allstate Employees, a 401(k) plan, pursuant to the most recent plan statement, dated December 21, 2004.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>MICHAEL J MC CABE</signatureName>
        <signatureDate>2004-12-22</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
