Alien is a science-fiction horror/action media franchise centered on the film series depicting warrant officer Ellen Ripley (Sigourney Weaver) and her battles with an extraterrestrial lifeform, commonly referred to as the Alien or Xenomorph. Produced and distributed by 20th Century Studios, the series began with Alien (1979), directed by Ridley Scott, and was followed by three sequels, Aliens (1986), Alien 3 (1992), and Alien Resurrection (1997), directed by James Cameron, David Fincher, and Jean-Pierre Jeunet, respectively.

Scott also directed a prequel series, composed of Prometheus (2012) and Alien: Covenant (2017), which follows the exploits of the David 8 android and the creators of the eponymous creatures referred to as the Engineers. The series has led to numerous novels, comics, and video game spin-offs. The Alien vs. Predator franchise combines the continuities of the Alien franchise with the Predator franchise and consists of two films as well as various series of comics, books, and video games.