William Barr (disambiguation)

William Barr (born 1950) is an American lawyer and government official.

William Barr may also refer to:
 * William G. Barr (1920–1987), Illinois state representative and businessman
 * William Barr (historian) (born 1940), Scottish historian at the University of Calgary, Canada
 * William Barr (artist) (1867–1933), Scottish / Californian artist
 * Billy Barr (footballer) (born 1969), English footballer and coach
 * Billy Barr (naturalist), famous for collecting 40 years of climate change data