<SUBMISSION>
<ACCESSION-NUMBER>0001179110-08-020960
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20081212
<FILING-DATE>20081216
<DATE-OF-FILING-DATE-CHANGE>20081216
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>AES CORP
<CIK>0000874761
<ASSIGNED-SIC>4991
<IRS-NUMBER>541163725
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>4300 WILSON BOULEVARD
<CITY>ARLINGTON
<STATE>VA
<ZIP>22203
<PHONE>7035221315
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4300 WILSON BOULEVARD
<CITY>ARLINGTON
<STATE>VA
<ZIP>22203
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>AES CORPORATION
<DATE-CHANGED>19930328
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>MORSE JOHN B JR
<CIK>0001018396
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12291
<FILM-NUMBER>081252777
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>C/O THE WASHINTON POST CO
<STREET2>1150 15TH ST NW
<CITY>WASHINGTON
<STATE>DC
<ZIP>20071
<PHONE>2029946694
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1150 15TH ST NW
<CITY>WASHINGTON
<STATE>DC
<ZIP>20071
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-12-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000874761</issuerCik>
        <issuerName>AES CORP</issuerName>
        <issuerTradingSymbol>AES</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001018396</rptOwnerCik>
            <rptOwnerName>MORSE JOHN B JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4300 WILSON BOULEVARD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ARLINGTON</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22203</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-12-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13220</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.27</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13220</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13220</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Amended and Restated Deferred Compensation Plan for Directors</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Amended and Restated Deferred Compensation Plan for Directors of The AES Corporation (the &quot;Company&quot;), Non Employee Directors may elect to defer receipt of annual cash compensation otherwise payable to such Director in the form of stock units on the day that the Non Employee Director is appointed to the Board of Directors for the plan year for which a stock unit election is made or on a date determined by the Board of Directors.  A Non Employee Director is not eligible to receive a distribution from his/her deferred account until such Director ceases to be a Board member.  This distribution will be made as soon as practicable after the date the Director terminates service on the Board, and will be made in accordance with the Director's Distribution Election Notification.  Each stock unit is the economic equivalent of one share of AES Common stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John B. Morse, Jr.</signatureName>
        <signatureDate>2008-12-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
