The Mercury Theater was a theater company founded in New York City in 1937 by Orson Welles and John Houseman. After initial success in live theatrical productions, in 1938 the Mercury Theater progressed into their their best-known period as The Mercury Theater on the Air, a radio series that included one of the most notable and infamous radio broadcasts of all time, The War of the Worlds, broadcast on October 30, 1938. The Mercury Theater on the Air produced live radio dramas in 1938-1940 and again briefly in 1946.

In addition to Welles and Houseman, The Mercury Theater troupe included Joseph Cotten, Martin Gabel, Vincent Price, Agnes Moorehead, Ray Collins, Hans Conreid, Paul Stewart, Will Geer, George Coulouris, Olive Stanton, and Everett Sloane. Much of the troupe would later appear in Welles' films at RKO, particularly Citizen Kane and The Magnificent Ambersons. Other future stars of the stage, screen, and television, like Betty Garrett, Anne Baxter, Judy Holliday, and Norman Lloyd, also appeared in productions in smaller parts.