William Capell may refer to:
William Capel (died 1515), Lord Mayor of London William Capell, 3rd Earl of Essex (1697–1743), 3rd Earl of Essex William Capell, 4th Earl of Essex (1732–1799), 4th Earl of Essex William Capel (sportsman) (1775–1854), sportsman and priest William Jennings Capell (born 1952), American heir presumptive to the earldom of Essex
See also William Kapell, pianist