Black Christmas (originally titled Silent Night, Evil Night in the United States and retitled Stranger in the House on television screenings) 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 mentally ill 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, and was distributed by Warner Bros. in North America.

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 its 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.