Her Majesty's Theatre is a West End theatre, in Haymarket, City of Westminster, London. The present building was designed by Charles J. Phipps and was constructed in 1897 for actor-manager Herbert Beerbohm Tree, who established the Royal Academy of Dramatic Art at the theatre. In the early decades of the 20th century, Tree produced spectacular productions of Shakespeare and other classical works, and the theatre hosted premières by major playwrights such as George Bernard Shaw, J. M. Synge, Noël Coward and J. B. Priestley. Since World War I, the wide stage has made the theatre suitable for large-scale musical productions, and the theatre has specialised in hosting musicals. The theatre has been home to record-setting musical theatre runs, notably the World War I sensation Chu Chin Chow and the current production, Andrew Lloyd Webber's The Phantom of the Opera, which has played continuously at Her Majesty's since 1986.

The theatre was established by architect and playwright John Vanbrugh, in 1705, as the Queen's Theatre. Legitimate drama unaccompanied by music was prohibited by law in all but the two London patent theatres, and so this theatre quickly became an opera house. Between 1711 and 1739, more than 25 operas by George Frederick Handel premièred here.[3] In the early 19th century, the theatre hosted the opera company that was to move to the Theatre Royal, Covent Garden, in 1847, and presented the first London performances of Mozart's La clemenza di Tito, Così fan tutte and Don Giovanni.[4] It also hosted the Ballet of her Majesty's Theatre in the mid-19th century, before returning to hosting the London premières of such famous operas as Bizet's Carmen and Wagner's Ring Cycle.

The name of the theatre changes with the sex of the monarch. It first became the King's Theatre in 1714 on the accession of George I. It was renamed Her Majesty's Theatre in 1837. Most recently, the theatre was known as His Majesty's Theatre from 1901 to 1952, and it became Her Majesty's on the accession of Elizabeth II. The theatre's capacity is 1,216 seats, and the building was Grade II* listed by English Heritage in January 1970. Really Useful Group Theatres has owned the theatre building since 2000. The land beneath it is on a long-term lease from the Crown Estate.