William Edgar Thornton (M.D.) (April 14, 1929 – January 11, 2021) was an American NASA astronaut. He was born in Faison, North Carolina. Thornton was a member of the astronaut support crew for the Skylab 2, 3, and 4 missions. A veteran of two space flights, Thornton spent over 313 hours in space. He was a mission specialist on STS-8 in 1983, and STS-51B in 1985.