Un Natale rosso sangue

Black Christmas is a 1974 Canadian slasher film produced and directed by Bob Clark, and written by Roy Moore. It stars Olivia Hussey, Keir Dullea, Margot Kidder, and John Saxon. The story follows a group of sorority sisters who receive threatening phone calls and are eventually stalked and murdered by a killer during the Christmas season.

Inspired by the urban legend "the babysitter and the man upstairs" and a series of murders that took place in the Westmount neighbourhood of Montreal, Quebec, Moore wrote the screenplay under the title Stop Me. The filmmakers made numerous alterations to the script, primarily the shifting to a university setting with young adult characters. It was shot in Toronto in 1974 on an estimated budget of $686,000.

The film was released in Canada by Ambassador Film Distributors on October 11, 1974. Warner Bros. released the film in the United States in May 1975 under the alternate title Silent Night, Evil Night, though this title was retracted and the film was reissued under its original title beginning August 6, 1975. The film went on to gross $4,053,000 worldwide.

Upon its release, Black Christmas received mixed reviews, but it has since received critical re-appraisal, with film historians noting it for being one of the earliest slasher films. It is also praised for its influence on John Carpenter's Halloween (1978). Aside from it earning a cult following since its release, a novelization written by Lee Hays was published in 1976. It is the first film in the Black Christmas series, being followed by two remakes in 2006 and 2019.