William Mortlock (18 July 1832 at Kennington, London – 23 January 1884 at Lambeth, London) was an English professional cricketer who played first-class cricket from 1851 to 1870. His brother Thomas was a first-class umpire. A right-handed batsman and slow underarm bowler who played for Surrey County Cricket Club, Mortlock made 191 known appearances in first-class matches. He represented the Players in the Gentlemen v Players series.