The Mercury Theatre on the Air was the radio home of Welles's ground-breaking Mercury Theatre Company. Following the success of Welles's radio adaptation of Hugo's Les Miserables, CBS requested a 13-episode run with Welles starring and directing, transferring the already well-regarded Mercury Theatre to the radio.

First broadcast at 9pm on July 11, 1938, the productions were hour-long adaptations of both classic and contemporary literature, often told in the first-person, and always featuring a 23-year-old Orson Welles in the starring role(s). Their success, which had always been more critical than popular, peaked with the notorious broadcast of H.G Wells’ War of the World on October 30, 1938, which was said to have sent hordes of credulous Americans fleeing from the cities.

Delighted though Welles no doubt was by this mischief, in spite of his fervent denials, it spelled the arrival of a large sponsor - Campbell’s Soup - who changed the name and began to apply their expertise in grey soup manufacturing to radio theatre. The degree of interference by Campbell's, which went far beyond their excruciating adverts interrupting the drama, led to a slow decline in quality and to Welles’s eventual departure. The theatre continued in various guises until the mid 1940s.