The Black Crook is a work of musical theatre first produced in New York City with great success in 1866. Many theatre writers have cautiously identified The Black Crook as the first popular piece that conforms to the modern notion of a musical. The book is by Charles M. Barras. The music, selected and arranged by Thomas Baker, consists mostly of adaptations, but it included some new songs composed for the piece, notably "You Naughty, Naughty Men". The story is a Faustian melodramatic romantic comedy, but the production became famous for its spectacular special effects and skimpy costumes.

Musical theatre is a form of theatrical performance that combines songs, spoken dialogue, acting and dance. The story and emotional content of a musical – humor, pathos, love, anger – are communicated through words, music, movement and technical aspects of the entertainment as an integrated whole. Although musical theatre overlaps with other theatrical forms like opera and dance, it may be distinguished by the equal importance given to the music as compared with the dialogue, movement and other elements. Since the early 20th century, musical theatre stage works have generally been called, simply, musicals.