The Mouse That Roared is a 1959 British satirical comedy film on a Ban The Bomb theme, based on Leonard Wibberley's novel The Mouse That Roared (1955). It stars Peter Sellers in three roles: Duchess Gloriana XII; Count Rupert Mountjoy, the Prime Minister; and Tully Bascomb, the military leader; and co-stars Jean Seberg. The film was directed by Jack Arnold, and the screenplay was written by Roger MacDougall and Stanley Mann.

Peter Sellers was an English actor and comedian. He first came to prominence performing in the BBC Radio comedy series The Goon Show. Sellers featured on a number of hit comic songs, and became known to a worldwide audience through his many film roles, among them Chief Inspector Clouseau in The Pink Panther series.