William Thomson Hay (6 December 1888 – 18 April 1949) was an English comedian who wrote and acted in a schoolmaster sketch that was popular all over the world, and later transferred to the screen, where he also played other authority figures with comic failings. His film Oh, Mr. Porter! (1937), made by Gainsborough Pictures, is often cited as the supreme British-produced film-comedy, and in 1938 he was the third highest-grossing star in the UK. Many famous comedians have acknowledged him as a major influence. Hay was also a keen amateur astronomer.