The Alien (also known as Xenomorph or Internecivus raptus "murderous thief" is a fictional endoparasitoid extraterrestrial species that is the eponymous antagonist of the Alien film series. The species made its debut in the film Alien (1979) and reappeared in the sequels Aliens (1986), Alien 3 (1992), and Alien Resurrection (1997), as well as the crossover films Alien vs. Predator (2004) and Aliens vs. Predator: Requiem (2007). It was also featured in cameo appearances in the Predator franchise entries Predator 2 (1990), Predators (2010), and The Predator (2018).
The Alien design is credited to Swiss surrealist and artist H. R. Giger, originating in a lithograph titled Necronom IV and refined for the series' first film, Alien. The practical effects for the Alien's head were designed and constructed by Italian special effects designer Carlo Rambaldi. The species' design and life cycle have been extensively augmented, sometimes inconsistently, throughout each film.
Similar creatures of a slightly different designs named the "Deacon" makes a brief appearance in the Ridley Scott film Prometheus (2012). Two species, one being a different but similar creature called a "Neomorph" and the other being a variation of the Xenomorph species appear in the sequel to Prometheus, Alien: Covenant (2017), which reveals the potential origin of the species.In addition, the Alien appears in various literature and video game spin-offs from the franchises.
Unlike many other extraterrestrial races in science fiction, the Aliens are not sapient "tool-makers"; they lack a technological civilization. They are predatory creatures with no higher goals than the propagation and self-preservation of their species. Like wasps or termites, Aliens are eusocial, with a single fertile queen breeding a caste of warriors, workers, or other specialists strains. The Aliens' biological life cycle involves traumatic implantation of endoparasitoid larvae inside living hosts; these "chestburster" larvae erupt from the host's body after a short incubation period, rapidly mature from juvenile into adulthood within hours, and seek out more hosts for implantation.