<SUBMISSION>
<ACCESSION-NUMBER>0001179110-04-005450
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20031210
<FILING-DATE>20040305
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>SIMON PROPERTY GROUP INC /DE/
<CIK>0001063761
<ASSIGNED-SIC>6798
<IRS-NUMBER>046268599
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>115 WEST WASHINGTON STREET
<CITY>INDIANAPOLIS
<STATE>IN
<ZIP>46204
<PHONE>3176361600
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>115 WEST WASHINGTON STREET
<STREET2>-
<CITY>INDIANAPOLIS
<STATE>IN
<ZIP>46204
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CORPORATE PROPERTY INVESTORS INC
<DATE-CHANGED>19980610
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>MAUTNER HANS C
<CIK>0001070947
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-14469
<FILM-NUMBER>04651627
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>C/O DREYFUS CORP
<STREET2>200 PARK AVENUE
<CITY>NEW YORK
<STATE>NY
<ZIP>10166
<PHONE>2129226000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>PGGM KROOSTWEG NOORD 149
<STREET2>POSTBUS 117
<CITY>3700 AC ZEIST NETHER
<STATE>P7
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-12-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001063761</issuerCik>
        <issuerName>SIMON PROPERTY GROUP INC /DE/</issuerName>
        <issuerTradingSymbol>SPG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001070947</rptOwnerCik>
            <rptOwnerName>MAUTNER HANS C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>33 ST. JAMES SQUARE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>SW1Y 4JS</rptOwnerZipCode>
            <rptOwnerStateDescription>NETHERLANDS</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President- International Div.</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Series B Preferred Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-12-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>26432</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-12-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>68354</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>354074</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person converted each share of Series B Preferred Stock into 2.58605 shares of Common Stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Hans C. Mautner, and his attorney-in-fact, Shelly Doran</signatureName>
        <signatureDate>2004-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>

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