Bill Moore, born William Leonard Moore in 1943, is an American author and UFO researcher who was among the field's most influential figures from the late 1970s to the late 1980s. He co-wrote the book that first popularized the 1947 Roswell case, was the original source of the Majestic-12 documents, and in 1989 told a UFO conference that he had cooperated with Air Force counterintelligence agents who were feeding false material to researchers.

Moore graduated from Thiel College in Greenville, Pennsylvania, in 1965 and taught language and humanities in high schools before becoming Arizona state section director of the Mutual UFO Network and turning to freelance writing. With Charles Berlitz he wrote The Philadelphia Experiment: Project Invisibility (1979) and The Roswell Incident (Grosset & Dunlap, 1980), which used accounts from retired intelligence officer Jesse Marcel and others to argue that the debris recovered in 1947 came from an extraterrestrial craft. Critics called the Roswell book "a collection of wild hearsay," the media scholar Barna William Donovan has written, but its version dominated the case until the late 1980s.

After the book, men presenting themselves as Air Force intelligence officers, among them AFOSI special agent Richard Doty, approached Moore, who said later that they recruited him with an unfulfilled promise of genuine government records. In 1982 he admitted that he had typed and stamped a "facsimile" of a memo referring to "MJ Twelve." In December 1984 his collaborator Jaime Shandera received an anonymous roll of film showing a purported briefing for President-elect Eisenhower, and Moore made the papers public in 1987 with Shandera and Stanton Friedman. After the Air Force reported that no such committee had been authorized, the FBI called the document "completely bogus," and critics found a Truman signature copied from a genuine 1947 letter and a date format common in Moore's own notes. Moore has suggested that the papers were a government disinformation exercise.

On July 1, 1989, at the MUFON symposium in Las Vegas, Moore gave a speech, taking no questions, in which he said he had passed information about fellow researchers to intelligence agents in the hope of receiving real inside material. He said he had supplied the agents with information about the Albuquerque businessman Paul Bennewitz while false material was fed to him, and acknowledged that some statements by the informants "Falcon" and "Condor" on the 1988 television special UFO Cover-Up? Live were untrue. The speech angered much of the audience, and Moore largely withdrew from the field.

His record drew new attention in 2026. In April, The Debrief's review of the documentary Saucers, Spooks and Kooks reported that the author Adam Gorightly had tried to reach Moore through the writer Greg Bishop, but that Moore did not seem interested and had not discussed the subject for many years. A 1993 interview Bishop recorded with him recirculated on X in October, and online researchers revisited his role in the MJ-12 documents, drawing on his archived papers, and in the backstory of the 1997 Alien Interview video. Moore remains the rare researcher who helped build two of ufology's foundational stories, Roswell and MJ-12, and then publicly admitted working with the agents who were feeding the field false information.