Alien is a 1979 science-fiction horror film directed by Ridley Scott and written by Dan O'Bannon. Based on a story by O'Bannon and Ronald Shusett, it follows the crew of the commercial space tug Nostromo, who encounter the eponymous Alien, a deadly and aggressive extraterrestrial set loose on the ship. The film stars Tom Skerritt, Sigourney Weaver, Veronica Cartwright, Harry Dean Stanton, John Hurt, Ian Holm, and Yaphet Kotto.