|Lord Mayor of London|
|Preceded by||Adam de Bury|
|Succeeded by||John Warde|
|Preceded by||John Ladle|
|Succeeded by||John Northampton|
His family came from Durham. He was apprenticed to John Lovekyn, a member of the Fishmongers Guild, and succeeded his master as alderman of Bridge Ward in 1368, becoming sheriff in 1370 and lord mayor in 1374. He was Member of Parliament for the City of London in 1371, 1376, 1377, and 1383 as one of the two aldermanic representatives of the city. 
He is said to have suppressed usury in the city during his term of office as mayor. His name frequently figures as advancing loans to Richard II. He supported the king's uncle John of Gaunt, 1st Duke of Lancaster in the city, where there was a strong opposition to John.
William Walworth worked for a time in the Customs House under Geoffrey Chaucer. In John Gardner's book "The Life and Times of Chaucer" Walworth is described as one of a number of important merchants, all friends of Alice Perrers, who used their influence with the king (Edward III). In his book Gardner says that according to complaints in the House of Commons, this group conspired to keep food prices up, lent money to the king at inflated interest, and through personal and financial influence persuaded the king to issue edicts profitable to themselves.
His most famous exploit was his encounter with Wat Tyler during the English peasants' revolt of 1381, in his second term of office as Lord Mayor. In June of that year, when Tyler and his followers entered south London, Walworth defended London Bridge against them. He was with Richard II when he met the insurgents at Smithfield, and killed the rebel leader with his baselard. The circumstances of the killing – including whether Walworth planned the attack or struck on the spur of the moment – have always been unclear.
Walworth raised the city bodyguard in the king's defence, for which service he was rewarded by knighthood and a pension. He subsequently served on two commissions to restore the peace in the county of Kent.
He died in 1385, and was buried in the church of St. Michael, Crooked Lane, of which he was a considerable benefactor. Sir William Walworth was the most distinguished member of the Fishmongers Guild, and he invariably figured in the pageants prepared by them when one of their members attained the mayoralty. He became a favorite hero in popular tales, and appeared in Richard Johnson's Nine Worthies of London in 1592.
William Walworth is commemorated with a statue on Holborn Viaduct, near the boundary of the City of London.
- List of Sheriffs of the City of London
- List of Lord Mayors of London
- City of London (elections to the Parliament of England)
- "Chronological list of aldermen: 1302-1400". British History Online. Retrieved 6 October 2016.
- The Life and Times of Chaucer, Barns & Noble Inc., 1977.