Ancient astronauts (or ancient aliens) refer to a pseudoscientific set of beliefs which holds 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.
The idea that ancient astronauts existed and visited Earth is not taken seriously by academics and archaeologists, who identify such claims as pseudoarchaeological and/or unscientific. It has received no credible attention in peer reviewed studies. When proponents of the idea present evidence in favor of their beliefs, it is often distorted or fabricated. Further, the history of thought surrounding the subject shows that proponents have adopted white supremacist beliefs to argue that indigenous cultures around the world were incapable of the feats of technology and culture that they achieved.
Well-known ancient astronauts proponents in the latter half of the 20th century who have written numerous books or appear regularly in mass media include Erich von Däniken, Zecharia Sitchin, Robert K. G. Temple, Giorgio A. Tsoukalos, David Hatcher Childress, Peter Kolosimo, and Mauro Biglino.
Various terms are used to reference claims about ancient astronauts, such as ancient aliens, ancient ufonauts, ancient space pilots, paleocontact, astronaut- or alien gods, or paleo- or Biblical-SETI (search for extraterrestrial intelligence).
Believers in such ancient astronaut stories often maintain that all or some humans are either descendants or creations of extraterrestrial intelligence who landed on Earth at some point in the ancient past. An associated idea is that human knowledge, religion, and culture came from extraterrestrial visitors in ancient times, in that ancient astronauts acted as a "mother culture".