Giorgio A. Tsoukalos (/ˈsuːkələs/; Greek: Γεώργιος Τσούκαλος; born 14 March 1978) is a Swiss-born writer, ufologist, television presenter and producer. He is a proponent of the pseudoarchaeological theory that ancient alien astronauts interacted with ancient humans. He is known for his appearances on the television series Ancient Aliens.