Oh! Calcutta! is an avant-garde, risqué theatrical revue created by British drama critic Kenneth Tynan. The show, consisting of sketches on sex-related topics, debuted Off-Broadway in 1969 and then in the West End in 1970. It ran in London for over 3,900 performances, and in New York initially for 1,314. Revivals enjoyed even longer runs, including a 1976 Broadway revival that ran for 5,959 performances, making the show the longest-running revue in Broadway history, the second longest-running revival, and the eighth longest-running Broadway show ever.

The Duchess Theatre is a West End theatre in the City of Westminster, London, located in Catherine Street near Aldwych.