Giorgio A. Tsoukalos is a Swiss-born writer, television presenter, and producer. He is a proponent of the pseudo-archaeological theory that ancient alien astronauts interacted with ancient humans. He is best known for his appearances on the television series Ancient Aliens.

Tsoukalos was born in Lucerne, Switzerland, in 1978. He is of Greek-Austrian heritage. He graduated from Ithaca College in Ithaca, New York, in 1998 with a bachelor's degree in communications. After graduating, he worked as a bodybuilding promoter and a volunteer in IFBB sanctioned bodybuilding contests, including Mr. Olympia. He produced and directed the annual IFBB San Francisco Pro Grand Prix from 2001 to 2005.

Since 2002, Tsoukalos has appeared in programs broadcast by Travel Channel, History, Syfy, and National Geographic. He was the editor of Legendary Times magazine from 1999 to 2008. In 2009, he began appearing as a regular on the History Channel series Ancient Aliens. He is also a co-executive producer of the show.

Tsoukalos's work has been criticized by many archaeologists and scientists, who argue that there is no evidence to support his claims of ancient alien visitation. However, Tsoukalos remains a popular figure among fans of the Ancient Aliens theory. He has written several books on the subject, including Chariots of the Gods Revisited (2002), Atlantis: The Evidence (2005), and The Lost Civilizations of Lemuria and Atlantis (2009).