William Kirby may refer to:
William Kirby (entomologist) (1759–1850), English entomologist William Kirby (author) (1817–1906), Canadian author William C. Kirby (born 1950), professor at Harvard University William F. Kirby (1867–1934), American politician William Forsell Kirby (1844–1912), English entomologist & folklorist William T. Kirby (1911–1990), businessman William Kirby (Gaelic footballer) (fl. 1990s–2010s), Gaelic footballer William Kirby (footballer, born 1883) (1883–1917), English footballer William Kirby (cricketer) (born 1981), English cricketer Bill Kirby (born 1975), Australian swimmer Cam Kirby or William J. Cameron Kirby (1909–2003), Canadian politician