Blow Out is a 1981 American independent mystery thriller film written and directed by Brian De Palma. The film stars John Travolta as Jack Terry, a movie sound effects technician from Philadelphia who, while recording sounds for a low-budget slasher film, unintentionally captures audio evidence of an assassination involving a presidential hopeful. Nancy Allen stars as Sally Bedina, a young woman involved in the crime. The supporting cast includes John Lithgow and Dennis Franz. The film's tagline in advertisements was, "Murder has a sound all of its own".

Directly based on Michelangelo Antonioni's 1966 film Blowup, the film replaces the medium of photography with one of audio recording. The concept of Blow Out came to De Palma while he was working on the thriller Dressed to Kill (1980). The film was shot in the late autumn and winter of 1980 in various Philadelphia locations on a budget of $18 million.

Blow Out opened to very little audience interest at the time of release despite receiving a mostly positive critical reception. The lead performances by Travolta and Allen, the direction by De Palma and the visual style were cited as the strongest points of the film. Critics also recognised the stylistic and narrative connection to the work of Alfred Hitchcock, whom De Palma admires, and giallo films. Over the years since its initial theatrical release, it has developed status as a cult film and received a home media release by the Criterion Collection, a company which specializes in "important classic and contemporary film," which re-ignited public interest in the film. Quentin Tarantino praises De Palma as the "greatest director of his generation" and cites Blow Out as one of his three favorite films that he would take to a desert island.