William Barr (disambiguation)

William Barr is an American lawyer and government official.
William Barr may also refer to:

William G. Barr, Illinois state representative and businessman
William Barr (historian), Scottish historian at the University of Calgary, Canada
William Barr (artist), Scottish / Californian artist
Billy Barr (footballer), English footballer and coach
Billy Barr (naturalist), American amateur scientist, known for collecting climate change data