X Minus One was an American half-hour science fiction radio drama series broadcast from April 24, 1955 to January 9, 1958 in various timeslots on NBC. Known for high production values in adapting stories from the leading American authors of the era, X Minus One has been described as one of the finest offerings of American radio drama and one of the best science fiction series in any medium.

Initially a revival of NBC's Dimension X (1950-51), the first 15 episodes of X Minus One were new versions of Dimension X episodes, but the remainder were adaptations by NBC staff writers, including Ernest Kinoy and George Lefferts, of newly published science fiction stories by leading writers in the field, including Isaac Asimov, Ray Bradbury, Philip K. Dick, Robert A. Heinlein, Frederik Pohl and Theodore Sturgeon, along with some original scripts by Kinoy and Lefferts. Included in the series were adaptations of Robert Sheckley's "Skulking Permit," Bradbury's "Mars Is Heaven", Heinlein's "Universe" and "The Green Hills of Earth", Pohl's "The Tunnel under the World", J.T. McIntosh's "Hallucination Orbit", Fritz Leiber's "A Pail of Air", and George Lefferts' "The Parade".