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. It was produced by Gordon Carroll, David Giler and Walter Hill through their company Brandywine Productions, and was distributed by 20th Century Fox. Giler and Hill revised and made additions to the script; Shusett was executive producer. The Alien and its accompanying artifacts were designed by the Swiss artist H. R. Giger, while concept artists Ron Cobb and Chris Foss designed the more human settings.

It has been consistently praised in the years since its release, and is considered one of the greatest films of all time.