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 plot follows 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. In 2023, a short-lived prequel television series, Grease: Rise of the Pink Ladies, debuted on Paramount+, lasting for only one season.

During the summer of 1958, greaser Danny Zuko and straight-laced Australian girl Sandy Olsson fall in love at the beach. As Sandy prepares to return home, she worries that she will never see Danny again, but he comforts her that the summer is "only the beginning" for them.

On the first day of his senior year at Rydell High School, Danny reconnects with the members of his greaser gang the T-Birds: Sonny, Putzie, Doody, and his best friend Kenickie. Sandy arrives at Rydell and is introduced to girls' gang The Pink Ladies—Marty, Jan and leader Betty Rizzo—by mutual friend Frenchy. At lunch, Danny and Sandy each separately describe their summer, unaware of the other's presence until Sandy mentions Danny's name, which the Pink Ladies recognize.

At a pep rally, Sandy, now a cheerleader, flirts with Tom, a football player. Kenickie arrives in "Greased Lightnin'", a heavily used car he plans on restoring to drag race it at Thunder Road. Rizzo and the Pink Ladies surprise Sandy by reuniting her with a shocked Danny. Sandy is thrilled, but Danny makes fun of her to maintain his tough image. Frenchy invites her to a sleepover with the other Pink Ladies that night to make her feel better.

At the sleepover, Rizzo makes fun of Sandy's good girl image and Frenchy announces she is dropping out of Rydell to go to beauty school. The T-Birds crash the party, and Rizzo leaves with Kenickie to have sex in Greased Lightnin' at a nearby make out spot. While the couple is there, rival greasers Leo and Cha-Cha interrupt them.

Danny motivates the T-Birds to work on the car by saying it will win them both girls and races. Later, he sees Sandy on a date with Tom and tries to apologize for his attitude at the pep rally, but she is unconvinced. Danny tries several sports in order to impress Sandy, eventually succeeding at track and field. Sandy, bored with Tom, agrees to be Danny's date to an upcoming dance at which the television show National Bandstand will do a live broadcast from the Rydell gym. Rizzo and Kenickie break up after a fight. After a disastrous beauty class, Frenchy reluctantly decides to return to Rydell to complete her high school education.