X Minus One was a science fiction radio drama that aired on NBC from April 24, 1955, to January 9, 1958, for a total of 124 episodes. The show struggled to find a large following due to occupying various time slots throughout its run. It was an extension of Dimension X, which aired from 1950-51. The show's stories were adapted from popular science fiction magazines of the time, Astounding and Galaxy. The adaptations were handled by writers Ernest Kinoy and George Lefferts, who also created original stories. Some episodes featured stories by famous authors like Ray Bradbury, Isaac Asimov, and Poul Anderson.

The program began with announcer Fred Collins delivering a countdown, followed by an introduction that set the stage for the futuristic adventures to come. The series was canceled after its 126th broadcast, and a revival attempt in the early 1970s with an experimental episode failed to bring back the show. However, the series was re-released in podcast form in 2007, and in 2008, Counter-Productions Theatre Company adapted and staged three episodes for theater.