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

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-04-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000100893</issuerCik>
        <issuerName>UNION PLANTERS CORP</issuerName>
        <issuerTradingSymbol>UPC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001181800</rptOwnerCik>
            <rptOwnerName>DOXEY BOBBY L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>P. O. BOX 387</rptOwnerStreet1>
            <rptOwnerStreet2>ATTN: LEGAL DIVISION</rptOwnerStreet2>
            <rptOwnerCity>MEMPHIS</rptOwnerCity>
            <rptOwnerState>TN</rptOwnerState>
            <rptOwnerZipCode>38147-</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President &amp; CFO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>82021</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-21</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1242</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2986</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(K)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-21</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>188</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>24.81</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-10-08</value>
            </exerciseDate>
            <expirationDate>
                <value>2012-10-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>125000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>125000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>25.5867</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-10-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-10-10</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>112500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>112500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>28.2267</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-12-28</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-03-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1512</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1512</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>28.2267</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-06-28</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-06-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>320</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>320</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>30.06</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-08-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-03-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8261</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8261</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>30.06</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-02-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-02-10</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2064</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2064</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.4533</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2002-10-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-03-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1821</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1821</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.4533</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-04-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2012-04-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>585</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>585</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Emp.Stock Option(right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.48</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-10-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2013-10-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>93750</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>93750</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qual. Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>18.3333</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-03-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-03-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18484</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18484</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qual. Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>22.92</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2003-12-20</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-12-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>63000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>63000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Reporting person acquired 1242 shares of common stock under the 401(K) Plan.  The information in this report is based on a plan statement as of April 21, 2004.</footnote>
        <footnote id="F2">Reporting person acquired 8 shares of common stock under the ESOP Plan.  The information in the report is based on a plan statement as of April 21, 2004.</footnote>
        <footnote id="F3">Reporting person acquired 8 shares of common stock under the ESOP Plan.  The information in this report is based on a plan statement dated as of April 21, 2004.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>E. James House, Jr./Rebecca Baggett</signatureName>
        <signatureDate>2004-04-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0201
4
2004-04-21
0
0000100893
UNION PLANTERS CORP
UPC
0001181800
DOXEY BOBBY L
P. O. BOX 387
ATTN: LEGAL DIVISION
MEMPHIS
TN
38147-
0
1
0
0
Executive Vice President & CFO
Common Stock
82021
D
Common Stock
2004-04-21
4
J
0
1242
0
A
2986
I
401(K)
Common Stock
2004-04-21
4
J
0
8
0
A
188
I
ESOP
Emp.Stock Option(right to buy)
24.81
2005-10-08
2012-10-08
Common Stock
125000
125000
D
Emp.Stock Option(right to buy)
25.5867
2004-10-10
2011-10-10
Common Stock
112500
112500
D
Emp.Stock Option(right to buy)
28.2267
2001-12-28
2010-03-01
Common Stock
1512
1512
D
Emp.Stock Option(right to buy)
28.2267
2004-06-28
2011-06-28
Common Stock
320
320
D
Emp.Stock Option(right to buy)
30.06
2004-08-10
2010-03-01
Common Stock
8261
8261
D
Emp.Stock Option(right to buy)
30.06
2005-02-10
2014-02-10
Common Stock
2064
2064
D
Emp.Stock Option(right to buy)
33.4533
2002-10-25
2010-03-01
Common Stock
1821
1821
D
Emp.Stock Option(right to buy)
33.4533
2004-04-25
2012-04-25
Common Stock
585
585
D
Emp.Stock Option(right to buy)
33.48
2004-10-14
2013-10-14
Common Stock
93750
93750
D
Non-Qual. Stock Option
18.3333
2001-03-01
2010-03-01
Common Stock
18484
18484
D
Non-Qual. Stock Option
22.92
2003-12-20
2010-12-20
Common Stock
63000
63000
D
Reporting person acquired 1242 shares of common stock under the 401(K) Plan.  The information in this report is based on a plan statement as of April 21, 2004.
Reporting person acquired 8 shares of common stock under the ESOP Plan.  The information in the report is based on a plan statement as of April 21, 2004.
Reporting person acquired 8 shares of common stock under the ESOP Plan.  The information in this report is based on a plan statement dated as of April 21, 2004.
E. James House, Jr./Rebecca Baggett
2004-04-22