Atlantis is the island power described by Plato in two dialogues, Timaeus and Critias, written around 360 BC. In the story, which Critias says reached Athens through the lawgiver Solon from Egyptian priests, Atlantis lay in the Atlantic beyond the Pillars of Heracles, was "larger than Libya and Asia together," and ruled an empire reaching into Europe and Africa. Some 9,000 years before Solon it attacked Athens, was defeated, and then vanished beneath the sea in a single day and night.

Present-day classicists and philologists agree that the account is fiction, most reading it as a vehicle for Plato's political philosophy, and debate centers on what inspired it, with the Bronze Age eruption of Thera, which devastated Minoan Crete, among the candidates. The modern idea of Atlantis as the lost source of all civilization dates to Ignatius Donnelly's 1882 book Atlantis: The Antediluvian World. Helena Blavatsky's Theosophy cast Atlanteans as an earlier "root race," and the clairvoyant Edgar Cayce claimed many of his subjects had been Atlanteans and that a "Hall of Records" lay beneath the Sphinx. Most such interpretations are classed as pseudohistory or pseudoarchaeology.

In 2026 the story re-entered UAP media through retired Rear Admiral Tim Gallaudet, a former Oceanographer of the Navy and acting head of NOAA. In a clip circulated in May, he said there was data "convincing that it existed" and that it met its end in a catastrophe around the Younger Dryas, about 12,900 years ago. On American Alchemy in August, he told Jesse Michels that a team of archaeologists and geologists had found a region in the Atlantic that "fits all of the descriptions in Plato's dialogs," based on high-resolution seafloor mapping, and Michels said Gallaudet planned to dive the site with the explorer who has reached the deepest point of every ocean. Writing on the ocean-science blog Southern Fried Science, Chris Parsons noted that ruins that old would lie under sediment and need "substantial geophysical analysis and literal digging" to confirm.

Gallaudet's claim joined a crowded field. Former CIA officer John Ramirez has linked the Cherokee Nation to Atlantis survivors, and The Why Files devoted an episode to the idea that the Basque people descend from Atlanteans. Because Gallaudet paired his search with accounts of craft moving between sea and sky, part of the wider debate over USOs and transmedium UAP, Atlantis became a meeting point for ocean UFO reports and lost-civilization history in 2026 media, while the scholarly view remains that Plato invented it.