Caliber 9 (Italian: Milano calibro 9) is a 1972 poliziottesco film written and directed by the Fernando Di Leo and starring Gastone Moschin, Mario Adorf and Barbara Bouchet. The film is based on a book 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 The Italian Connection in 1972 and Il Boss (The Boss) in 1973.