Grease is a 1978 American musical romantic comedy film directed by Randal Kleiser (in his feature directorial debut) from a screenplay by Bronté Woodard and an adaptation by co-producer Allan Carr, based on the 1972 stage musical of the same name by Jim Jacobs and Warren Casey. The film depicts the lives of greaser Danny Zuko (John Travolta) and Australian transfer student Sandy Olsson (Olivia Newton-John), who develop an attraction for each other during a summer romance.

Grease was released in the United States on June 16, 1978, by Paramount Pictures. The film was successful both critically and commercially, becoming the highest-grossing musical film at the time. Its soundtrack album ended 1978 as the second-best-selling album of the year in the United States, only behind the soundtrack of the 1977 film Saturday Night Fever, which also starred Travolta, and the song "Hopelessly Devoted to You" was nominated for an Academy Award for Best Original Song at the 51st Academy Awards. The film also received five nominations at the 36th Golden Globe Awards, including for Best Motion Picture – Musical or Comedy and two for Best Original Song, for "Grease" and "You're the One that I Want". In 2020, Grease was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".

A sequel, Grease 2, was released in 1982, starring Maxwell Caulfield and Michelle Pfeiffer as a newer class of greasers. Few of the original cast members reprised their roles. As of 2023, a short-lived prequel television series, Grease: Rise of the Pink Ladies, debuted on Paramount+, with a prequel film, titled Summer Lovin', currently in production.