Giorgio A. Tsoukalos is a Swiss-born writer, television presenter and producer, best known as the featured guest and co-executive producer of Ancient Aliens on the History Channel. Born in Lucerne in 1978 and of Greek-Austrian heritage, he promotes the ancient-astronaut hypothesis, the idea that extraterrestrial visitors influenced early human civilizations, and has become the most recognizable television face of that idea.

Tsoukalos graduated from Ithaca College in 1998 with a bachelor's degree in communications. From 1999 to 2007 he worked as a promoter for bodybuilding contests sanctioned by the International Federation of Bodybuilding and Fitness, including Mr. Olympia, and from 1999 to 2008 he edited Legendary Times, a magazine devoted to ancient-astronaut research. From 2002 he appeared on programs for the Travel Channel, History, Syfy and National Geographic, among them three episodes of UFO Hunters in 2009.

Ancient Aliens began as a two-hour History special on March 8, 2009, and became a series the following year. Produced by Prometheus Entertainment, it moved to the sister channel H2 from 2012 to 2014 before returning to History, and its 22nd season began in January 2026. The show draws on the hypothesis popularized by Erich von Däniken in Chariots of the Gods? and presents monuments, myths and religious texts as possible traces of ancient contact. Tsoukalos appears in nearly every episode and also presented and co-produced In Search of Aliens for H2 in 2014. His appearances inspired the internet meme captioned "I'm not saying it was aliens ... but ...", which circulated from late 2010; in a 2015 Reddit question-and-answer session he called it "a great honor to have been embraced" by internet users.

Historians, archaeologists and other scientists have criticized the series for presenting pseudoscience and pseudohistory as fact. Writing in Smithsonian in 2012, Riley Black said its episodes overwhelm viewers with "fictions and distortions" in a rapid-fire Gish gallop. Kenneth Feder, a professor of archaeology at Central Connecticut State University, said that when producers invited him to appear he told them he rejected the hypothesis outright, and that he never heard back. The skeptic Brian Dunning called the show "a slap in the face to the ingenuity of the human race," and Dictionary.com said the meme mimicked Tsoukalos's tone of conviction in presenting "unfounded far-fetched pseudo-logic as fact."

In June 2026 Tsoukalos turned that skepticism on the modern disclosure movement. After the June 9 press conference on the Capitol steps, where David Grusch appeared with four members of Congress, he posted that the participants offered talk of "irrefutable evidence" without "receipts" and told them to "SHOW THE EVIDENCE or shut up already." Matt Ford of The Good Trouble Show replied that nobody at the event had said "irrefutable evidence," citing the transcript and five recordings, and invited Tsoukalos onto his show. The exchange set the best-known face of televised alien-contact theory against the whistleblower and the lawmakers pressing Congress for UAP records.