Caliber 9 (Milano calibro 9) is a poliziottesco film written and directed by the Italian crime film specialist Fernando Di Leo in 1972. The film is based on a novel of the same name written by Giorgio Scerbanenco.

The soundtrack for the film, Preludio Tema Variazioni e Canzona, is a collaboration album between Luis Enríquez Bacalov and the Italian progressive rock group Osanna.

Milano calibro 9 is the first part in Di Leo's Milieu Trilogy. The film was followed by La mala ordina (Manhunt) in 1972 and by Il boss (The Boss) in 1973

The Plot:
In the first film of the Fernando Di Leo triology, small-time gangster Ugo Piazza has just been released from prison. He tries to convince the police, the mafia, and his one-time associate Rocco, a sadistic hoodlum who enjoys sick violence and torture, that he wants to go straight, but everyone believes he has $300,000 of stolen money hidden somewhere. Caliber 9’s stylized violence, fast-paced action sequences, tight editing and plot twists prefigure the work of Quentin Tarantino and John Woo. The film also features a notable score by Luis Bacalov and the stunning Barbara Bouchet as Ugo’s go-go dancing girlfriend.