Ancient Aliens is an American television series produced by Prometheus Entertainment that explores the pseudoscientific hypothesis of ancient astronauts in a non-critical, documentary format. Episodes also explore related pseudoscientific and pseudohistoric topics, such as: Atlantis and other lost ancient civilizations, extraterrestrial contact and ufology, and popular conspiracy theories. The series, which has aired on History since 2010, has been a target for criticism of History's channel drift, as well as criticism for promoting unorthodox or unproven hypotheses as fact. According to Smithsonian, episodes of the series overwhelm the viewer with "fictions and distortions" by using a Gish gallop.

Ancient astronauts refer to a pseudoscientific set of beliefs that hold that intelligent extraterrestrial beings visited Earth and made contact with humans in antiquity and prehistoric times. Proponents suggest that this contact influenced the development of modern cultures, technologies, religions, and human biology. A common position is that deities from most, if not all, religions are extraterrestrial in origin, and that advanced technologies brought to Earth by ancient astronauts were interpreted as evidence of divine status by early humans.