William Joseph "Billy" Baldwin is an American actor. A member of the Baldwin family, he is the second-youngest Baldwin of the four Baldwin brothers. He has starred in the films Flatliners (1990), Backdraft (1991), Sliver (1993), Virus (1999), The Squid and the Whale (2005), Forgetting Sarah Marshall, in which he portrayed himself, and the Netflix show Northern Rescue (2019). Baldwin is married to singer Chynna Phillips.

Virus is a 1999 American science fiction horror film directed by visual effects artist John Bruno and starring Jamie Lee Curtis, William Baldwin and Donald Sutherland. Based on the comic book of the same name by Chuck Pfarrer, it tells the story of a ship beset by a malevolent extraterrestrial entity that seeks to turn humanity into cyborg slaves.