Alien or Aliens may mean:

• Extraterrestrial life, in scientific context
• Extraterrestrial life in culture
• Alien (biology), a non-native species
• Alien (computing), a program that converts between different Linux package distribution file formats
• Alien (law), a person who is neither a native nor a citizen of their country of residence
• Alien (signifier), use in literature and criticism as the embodiment of an outside perspective or the sense of the other
• Alien (film) (1979 film), by Ridley Scott, which inspired the following related works:
  • Aliens (1986 film), the sequel to the 1979 film
  • Alien³ (1992 film), the third Alien movie
  • Resurrection (1997 film), the fourth Alien movie
  • Alien vs. Predator (2004 film), also a comic book series, novel series, and video game series
  • Alien vs. Predator 2 (2007 film)
  • Xenomorph (Alien), the alien creatures from the Alien movies
  • Aliens (comic), a group of comic book series
• The Aliens, Roky Erickson's backing band
• Alien (game), a 1984 DOS text adventure
• Aliens (video game), referring to a number of video games
• Aliens (arcade game), a 1990 arcade shoot 'em up by Konami
• Aliens (album), an album by Irish celtic rock band Horslips
• Alienware Computer Corporation, a division of Dell

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