West Side Story is an American musical with a book by Arthur Laurents, music by Leonard Bernstein, and lyrics by Stephen Sondheim. The musicals plot and story is based on William Shakespeares Romeo and Juliet.

Set in New York City in the mid-1950s, the musical explores the rivalry between the Jets and the Sharks, two teenage street gangs of different ethnic (ethnicity) and cultural backgrounds. The members of the Sharks are first-generation Americans from Puerto Rico taunted by the Jets, a working-class white group who consider themselves the true Americans. The young protagonist, Tony, one of the Jets, falls in love with Maria, the sister of Bernardo, the leader of the Sharks. The dark theme, sophisticated music, extended dance scenes, and focus on social problems marked a turning point in American musical theatre. Bernsteins score for the musical has become extremely popular; it includes "Somethings Coming", "Maria (Maria (1956 song))", "America (America (West Side Story song))", "Somewhere (Somewhere (song))", "Tonight (Tonight (1956 song))", "Jet Song", "I Feel Pretty", "One Hand, One Heart", "Gee, Officer Krupke" and "Cool (Cool (Leonard Bernstein song))".

The original 1957 Broadway production, directed and choreographed by Jerome Robbins and produced by Robert E. Griffith and Harold Prince, marked Stephen Sondheims Broadway debut. It ran for 732 performances (a successful run for the time), before going on tour. The production garnered a Tony Award nomination for Best Musical in 1957, but the award went to Meredith Willsons The Music Man. It won a Tony Award in 1957 for Robbins choreography. The show had an even longer-running London production, a number of revivals and international success. The production spawned an innovative, award-winning 1961 musical film of the same name (West Side Story (film)), directed by Robert Wise and Robbins, and starring Natalie Wood, Richard Beymer, Rita Moreno, George Chakiris and Russ Tamblyn. It won ten Academy Awards out of eleven nominations.

West Side Story is produced frequently by schools, regional theatres, and occasionally by opera companies.