William Hart, also Will, Willy, Bill, or Billy Hart may refer to:
Arts and entertainment
William Hart (actor) (died 1650), English Caroline actor
William Hart (painter) (1823–1894), Scottish-American painter
William Hart (singer) (1945–2022), American soul singer, member of The Delfonics
William Matthew Hart (1830–1908), British lithographer and bird artist
William S. Hart (1864–1946), American silent film actor, screenwriter, director, and producer William Sterling Hart (1917–2006), American actor, better known as Robert Sterling Will Cullen Hart (born 1971), American musician and artist Billy Hart (born 1940), American jazz drummer
Judiciary
William Hart of Livelands, Scottist jurist and 16th century Lord Advocate
William H. H. Hart (1848–1903), American California attorney general
William L. Hart (1867–1962), American justice of the Supreme Court of Ohio
William Thomas Hart (1929-2023), United States federal judge
Sports
Bill Hart (footballer) (1923–1990), English professional footballer
Bill Hart (infielder) (1913–1968), American professional baseball third-baseman with the Brooklyn Dodgers Bill Hart (pitcher) (1865–1936), American professional baseball pitcher Billy Hart (baseball) (1866–1944), American professional baseball player
Other fields
William Hart (bishop) (1904–1992), Bishop of Dunkeld
William Hart (Medal of Honor) (1866–1899), American sailor
William Hart (MP), MP for Bletchingley
William Hart (police chief) (1924–2003), Detroit Police Chief
William Hart (politician) (1825–1904), Tasmanian businessman
William Hart (priest) (1558–1583), Catholic martyr
William Hart, drilled the first natural gas well in the US, leading to the Fredonia Gas Light Company's formation William C. Hart (1898–1963), United States Coast Guard member awarded the Gold Lifesaving Medal William E. Hart (1843–1874), Union Army soldier during the American Civil War William Ewart Hart (1885–1943), Australian aviator and dentist William Neville Hart (1741–1804), British banker, politician and diplomat William Stanford Hart Sr. (1925–1999), mayor of East Orange, New Jersey
Fictional characters
Bill Hart (comics), the civilian identity of the Lev Gleason Publications and Image Comics superhero Daredevil