William Trench may refer to:
William Trench, 1st Earl of Clancarty (1741–1805), Anglo-Irish aristocrat and politician William Trench, 3rd Earl of Clancarty (1803–1872), Irish nobleman William Trench III (1831–1896), reeve of Richmond Hill, Ontario William Le Poer Trench (1837–1920), Anglo-Irish politician and British army officer