William Mercer may refer to:
Sports Billy Mercer (rugby league) (1905–1965), rugby league footballer of the 1930s for England and St Helens RLFC William Mercer (cricketer) (1922–1989), English cricketer Willie Mercer (1874–1932), Scottish footballer
Others William Mercer (poet) (c. 1605–c. 1675), Scottish poet and army officer William Thomas Mercer (1821–1879), British Colonial Secretary in Hong Kong, 1859–1868 William W. Mercer (born 1964), American politician from Montana and former United States Attorney William (Rosko) Mercer (1927–2000), known as Rosko, American news announcer and disc jockey Bill Mercer (1926–2025), American sportscaster William Mercer (Australian politician) (1796–1871), British Army officer, landowner, pastoralist, and politician in colonial New South Wales
See also Billy Mercer (disambiguation)