David Huggins, 72, who creates oil paintings of his many alleged encounters with extraterrestrials, makes the shocking claims in new documentary Love and Saucers.
He described how he was 17 when an alien named Crescent seduced him after haunting him in his sleep.
They soon became an item and regularly had sex, he said.
But Crescent is no oil painting, according to the image Mr Huggins holds up when describing his nights of passion, saying proudly: “virginity lost”.
The film opens with David, from Hoboken, New Jersey, United States, making the bold claim: “When I was 17 I lost my virginity to a female extraterrestrial.”
David claimed after moving to New York to study art, he was haunted by Crescent in his sleep, and they became an item, regularly having sex.
The pairing even resulted in her giving birth to an alien/human hybrid, although there is no further detail on what became of the child.
David is consumed by the alien/UFO subject, and his living room is filled with books and about 2,000 videos.
His obsession was sparked by a 1965 Dr Who episode called The Web Planet, which features giant alien ants.
But, he claims his first encounter with an alien was aged seven or eight.
He grew up on a remote Georgia farm, but he was put off from religion after being taken to a hardline Christian church.
The first creature he claims to have seen was a “short, glowing-eyed, hairy guy”, which ran into woods.
Not long after he was sprayed with a grey sticky liquid by a praying mantis-like humanoid, he claims.
The mantis beings are an alleged race of alien visitors according to ET believers.
During the Fifties, he claims his childhood consisted of a series of bizarre encounters, including alien greys, and a “tall Nordic-like human-like being” who “was in charge of the mantis”.
They greys and “Nordics” or “Tall Whites” are other examples of alleged alien species identified by believers.
Jeffrey Kripal, a professor of Philosophy and Religious Thought at Rice University, Texas, believes David is sincere in his claims and is “just telling the truth”.
He sees David’s encounters in the same context as a religious or sacred experience, so similar to blind faith.
British UFO researcher Nigel Watson, author of The UFO Investigations Manual, said: “Unlike other documentaries that have an agenda to prove or disprove the existence of UFOs, or that subtly coach their subjects to look or sound ridiculous, director Brad Abrahams simply allows David to tell his intimate, fascinating and incredible story.”
Love and Saucers is directed by Brad Abrahams and its UK release date is to be confirmed.