M is a 1931 German mystery suspense thriller film directed by Fritz Lang and starring Peter Lorre as Hans Beckert, a serial killer who targets children. An early example of a procedural drama, the film centers on the manhunt for Lorre's character, conducted by both the police and the criminal underworld.

Friedrich Christian Anton Lang, better known as Fritz Lang, was an Austrian-American film director, screenwriter, and producer who worked in Germany and later the United States. One of the best-known émigrés from Germany's school of Expressionism, he was dubbed the "Master of Darkness" by the British Film Institute. He has been cited as one of the most influential filmmakers of all time.