The terms alien abduction or abduction phenomenon describe "subjectively real memories of being taken secretly against one’s will by apparently nonhuman entities and subjected to complex physical and psychological procedures." People claiming to have been abducted are usually called "abductees" or "experiencers." Typical claims involve being subjected to a forced medical examination that emphasizes their reproductive system. Abductees sometimes claim to have been warned against environmental abuse and the dangers of nuclear weapons. While many of these purported encounters are described as terrifying, some have been viewed as pleasurable or transformative.

Due to a lack of any substantial physical evidence, most scientists and mental health professionals dismiss the phenomenon as "deception, suggestibility (fantasy-proneness, hypnotizability, false-memory syndrome), personality, sleep phenomena, psychopathology, psychodynamics [and] environmental factors.". Skeptic Robert Sheaffer also sees similarity between the aliens depicted in early science fiction films, in particular, Invaders From Mars, and those reported to have actually abducted people.