The Man Called X is an espionage radio drama that aired from July 10, 1944, to May 20, 1952, on CBS and NBC. It starred British actor Herbert Marshall as Ken Thurston, an American intelligence agent who undertook dangerous cases in exotic locations. The series followed Ken as he unraveled mysteries and faced intrigue, danger, and romance around the world.

The show also featured Leon Belasco as Ken's comedic sidekick, Pegon Zellschmidt, who often turned up in remote parts of the world, either helping or annoying Ken. Announcers for the program included Jack Latham and Wendell Niles, while background music was provided by orchestras led by Milton Charles, Johnny Green, Felix Mills, and Gordon Jenkins. The Man Called X was created by Jay Richard Kennedy and later adapted into a television series (1956-1957) starring Barry Sullivan as Thurston.

Throughout its run, the show was sponsored by companies like Frigidaire and General Motors, and featured a rotating cast of talented radio actors such as Cathy Lewis, Peter Leeds, Lawrence Dobkin, and William Conrad. With its engaging plots, captivating characters, and exceptional music, The Man Called X remains an entertaining radio drama for fans of spy thrillers and classic radio shows.