William Percy may refer to:

• William de Percy (d.c. 1096/9), Anglo-Norman nobleman, crusader and founder of Whitby Abbey
• William Percy (c.1337-1407), MP for Sussex
• William Percy (bishop) (1428–1462), British bishop
• William Percy (writer) (1574–1648), English poet and playwright
• William Percy (portrait artist) (1820–1903), of Manchester, England
• William Henry Percy (1788–1855), British naval officer
• William Alexander Percy (politician), (1834–1888) American politician and grandfather of the below
• William Alexander Percy (1885–1942), American lawyer, planter and poet
• William Armstrong Percy III (born 1933), American historian and gay activist