Jim Jacobs (born October 7, 1942) is an American actor, composer, lyricist, and writer for the theatre, long associated with the Chicago theater scene. Jacobs is best known for creating the book, storyline, characters, lyrics for the 1971 musical Grease with Warren Casey. Grease would later be adapted into the film Grease in 1978, which would become one of the most successful film adaptations of a musical in history in terms of gross revenue adjusted for inflation.