Extraterrestrial, as an adjective, refers to something that originates, occurs, or is located outside Earth or its atmosphere. As a noun, the term is used to refer to any life form which comes from outside Earth and its atmosphere.

The term has been widely used in scientific circles for a long time, but was brought to the forefront of public attention by the film E.T. the Extra-Terrestrial, one of the most popular films of all time.