<ownershipDocument><schemaVersion>X0101</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-07-25</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000737468</issuerCik><issuerName>WASHINGTON TRUST BANCORP INC</issuerName>        <issuerTradingSymbol>WASH</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001212012</rptOwnerCik><rptOwnerName>KENNARD MARY E</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>  </rptOwnerStreet1><rptOwnerStreet2>  </rptOwnerStreet2><rptOwnerCity>  </rptOwnerCity><rptOwnerState>  </rptOwnerState><rptOwnerZipCode>  </rptOwnerZipCode></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-25</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>716</value></transactionShares><transactionValue><value>24.6</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>712.9097</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Andrew C. Robinson (son)</value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-25</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>716</value></transactionShares><transactionValue><value>24.6</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>712.9097</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>Charles A. Robinson (son)</value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">The reporting person also holds direct ownership interests in 1,047.2048 shares of common stock.  In addition to common stock holdings, the reporting person has the right to purchase 1,470 shares of common stock exercisable at $5.432 with an expiration date of 3/17/2004, 5,063 shares of common stock exercisable at $9.3333 with an expiration date of 4/30/2006, 1,688 shares of common stock exercisable at $12.1667 with an expiration date 4/29/2007, 1,688 shares of common stock exercisable at $21.3333 with an expiration date of 4/28/2008, 1,688 shares of common stock exercisable at $19.50 with an expiration date of 4/27/2009, 2,000 shares of common stock exercisable at $15.50 with an expiration date of 4/25/2010, 2,000 shares of common stock exercisable at $17.85 with an expiration date of 4/24/2011, 2,000 shares of common stock exercisable at $20.23 with an expiration date of 4/23/2012 and 2,000 shares of common stock exercisable at $20.62 with an expiration date of 4/29/2013.</footnote></footnotes><ownerSignature><signatureName>David V. Devault EVP, Treas, CFO-POA</signatureName><signatureDate>2003-07-25</signatureDate></ownerSignature></ownershipDocument>
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X0101
4
2003-07-25
0
0000737468
WASHINGTON TRUST BANCORP INC
WASH
0001212012
KENNARD MARY E
1
0
0
0
Common Stock
2003-07-25
4
S
0
716
24.6
D
712.9097
I
Andrew C. Robinson (son)
Common Stock
2003-07-25
4
S
0
716
24.6
D
712.9097
I
Charles A. Robinson (son)
The reporting person also holds direct ownership interests in 1,047.2048 shares of common stock.  In addition to common stock holdings, the reporting person has the right to purchase 1,470 shares of common stock exercisable at $5.432 with an expiration date of 3/17/2004, 5,063 shares of common stock exercisable at $9.3333 with an expiration date of 4/30/2006, 1,688 shares of common stock exercisable at $12.1667 with an expiration date 4/29/2007, 1,688 shares of common stock exercisable at $21.3333 with an expiration date of 4/28/2008, 1,688 shares of common stock exercisable at $19.50 with an expiration date of 4/27/2009, 2,000 shares of common stock exercisable at $15.50 with an expiration date of 4/25/2010, 2,000 shares of common stock exercisable at $17.85 with an expiration date of 4/24/2011, 2,000 shares of common stock exercisable at $20.23 with an expiration date of 4/23/2012 and 2,000 shares of common stock exercisable at $20.62 with an expiration date of 4/29/2013.
David V. Devault EVP, Treas, CFO-POA
2003-07-25