William Irwin or Bill Irwin may refer to:
- Bill Irwin (wrestler) (born 1954), American professional wrestler
- Bill Irwin (born 1950), American actor and clown
- Bill Irwin (footballer) (born 1951), Northern Irish ex-footballer
- Billy Irwin (Australian rules footballer) (1884–1946), Australian footballer
- Bill Irwin (priest) (1928–2004), Canadian priest
- Bill Irwin (baseball) (1859–1933), baseball player
- Bill Irwin (skier) (1920–2013), former Canadian skier
- Will Irwin (1873–1948), American author
- William Irwin (California politician) (1827–1886), California politician from the Democratic Party
- William Andrew Irwin (1884–1967), theologian
- William Arthur Irwin (1898–1999), Canadian journalist and diplomat
- William C. K. Irwin (1907–1998), a.k.a. Will Irwin, American pianist, conductor, and songwriter
- William Irwin (philosopher) (born 1970), professor of philosophy at King's College in Wilkes-Barre, Pennsylvania
- William Irwin (boxer) (born 1968), Canadian boxer
- William Irwin (Unionist politician) (born 1956), Unionist politician in Northern Ireland
- William W. Irwin (1803–1856), Mayor of Pittsburgh
- William W. Irvin or Irwin (1778–1842), Ohio politician
- William Roy Irwin (1898–1969), Canadian-born World War I flying ace