Dulce Base is the name given to a secret underground facility that some UFO writers say lies beneath Archuleta Mesa, a flat-topped mountain overlooking Dulce, New Mexico. Dulce, a town of about 2,800 in Rio Arriba County, is the headquarters of the Jicarilla Apache Nation, whose reservation land is at the center of the story. In the legend, aliens and the U.S. government jointly run a base where humans are used in experiments. No government record or physical trace has shown that any such base exists, and the skeptic Brian Dunning has noted that imagery of the mesa shows none of the buildings its promoters describe.

The story began with Paul Bennewitz, an Albuquerque businessman who from 1979 believed he was intercepting alien signals near Kirtland Air Force Base. After 1980 hypnosis sessions with a woman who described an underground facility, he came to believe aliens had a base near Dulce, and in a December 1981 letter to Senator Pete Domenici he described a conflict there in "late 79 or first of 80" and claimed a deal had traded Jicarilla Apache land for alien technology. Air Force agent Richard Doty later said he had fed false information to researchers, Bennewitz among them, and the researcher William Moore said in 1989 that he had done the same. By 1987 the aviator John Lear was promoting the base, and a writer publishing as Jason Bishop III later admitted inventing Dulce stories.

In 1995 lectures Phil Schneider said he had survived a 1979 firefight with aliens beneath the mesa; no record supports his story or the credentials he claimed. Gabe Valdez, the state police officer in Dulce who investigated cattle mutilation reports there in the late 1970s, rejected an alien explanation, saying, "predators don't leave gas masks, glow sticks, radar chaff." The scholar Michael Barkun has written that Cold War underground missile installations gave such rumors "superficial plausibility."

In 2016 the Santa Fe New Mexican reported that some tribal members described unexplained lights while others dismissed the legend, and that Council President Ty Vicenti had embraced it partly to draw visitors to an economically depressed area. That May a local nonprofit, Apache Indigenous Defenders, held a Dulce Base UFO conference at the Wild Horse Casino to raise money for groups that keep Native traditions alive. In 2026 the legend circulated mainly through reposted 1990s texts on Reddit. Dulce Base remains a legend that took shape during an admitted campaign of false information and has attached itself to a real community's land.