The Mariinsky Theatre (Russian: Мариинский театр, romanized: Mariinskiy teatr, also transcribed as Maryinsky or Mariyinsky) is a historic opera house in Saint Petersburg, Russia.

Opened in 1860, it became the preeminent music theatre of late 19th-century Russia, where many of the stage masterpieces of Tchaikovsky, Mussorgsky, and Rimsky-Korsakov received their premieres.

The theatre's name has changed throughout its history, reflecting the political climate of the time: Note: The acronym "GATOB" (Gosudarstvennïy Akademicheskiy Teatr Operï i Baleta) is often encountered in historical accounts.

Other notable productions included Rimsky-Korsakov's opera The Golden Cockerel in 1909 and Prokofiev's ballet Cinderella in 1946 (with Natalya Dudinskaya).

In April 2022, resident conductor Gavriel Heine, a protégé of Gergiev, resigned from the theater in part because of the 2022 Russian invasion of Ukraine.

[6] The nearby Mariinsky Theatre Concert Hall, designed by French architect, Xavier Fabre, opened in spring 2007.

The completion of Mariinsky II was predicted to result in Saint Petersburg's equivalent of New York City's Lincoln Center.