The X-Files is an American science-fiction drama created by Chris Carter for Fox. It follows FBI special agents Fox Mulder, a believer in the paranormal played by David Duchovny, and Dana Scully, a medical doctor and skeptic played by Gillian Anderson, as they work cases the bureau files as unexplained. About a third of its episodes follow a "mythology" arc in which the agents uncover a government conspiracy hiding evidence of extraterrestrial life and a planned alien invasion; the rest are stand-alone "monster of the week" stories.

The series ran from September 10, 1993, to May 19, 2002, across nine seasons and 202 episodes, with feature films in 1998 and 2008 and revival seasons of six episodes in 2016 and ten in 2018. Carter, a former surfing-magazine editor who joined Fox in 1992, drew on Kolchak: The Night Stalker, his youth during the Watergate scandal and a survey associated with psychiatrist John E. Mack suggesting that millions of Americans believed they might have been abducted. Its opening sequence ended with "The Truth Is Out There," and Mulder's office poster reading "I Want to Believe" was donated to the Smithsonian's National Museum of American History in 2008. By 2002 it was the longest-running consecutive American broadcast science-fiction series.

The show is fiction, but its language and imagery shaped how audiences talk about UFOs and official secrecy. Richard Dawkins criticized it in 1998 for promoting an anti-rational worldview, and writers Glen Morgan and James Wong said in 2018 that it likely helped bring conspiracy theories into the mainstream. Carter wrote in 2021 that the show's catchphrases came from a period of "relatively shared reality" and that "The slogans are now a fact of life." Its influence ran alongside other 1990s conspiracy dramas such as NBC's Dark Skies.

The franchise now belongs to Disney, which acquired 21st Century Fox's entertainment businesses. Ryan Coogler began developing a reboot in 2023, and Hulu ordered his pilot in February 2026, casting Danielle Deadwyler and later Himesh Patel as FBI agents assigned to a long-shuttered division for unexplained cases; Jennifer Yale is showrunner, and Carter holds an executive producer credit. The pilot filmed in Vancouver in May 2026, and Hulu ordered a full series on October 13, 2026. More than three decades after its premiere, The X-Files remains the reference point that UFO commentators, skeptics and fans reach for when describing government cover-up.