The Azerbaijan State Academic Opera and Ballet Theatre, formerly known as the Mailov Theatre is an opera house in Baku, Azerbaijan. It was built in 1911 at the request of magnate Daniel Mailov and funded by magnate Zeynalabdin Taghiyev.

The Russian architect and civil engineer of Armenian descent Nikolai Bayev designed the architectural sketch of the theatre. However the construction of such grandiose building in a year was unheard of at the time and required many safety measures to be taken. The three-shift work at the site involving 200 workers ensured speedy construction of the building. All works were completed in less than 10 months. The city mayor Peter Martynov accompanied by architects and engineers examined the newly built theatre and confirmed its safety. The official opening of the Mailyovs' Theatre was scheduled on 28 February 1911. Daniel Mailov notified Nezhdanova of the ceremony by telegramme beforehand, and the renowned soprano became the first singer to perform at the new opera house. Most of Baku's multiethnic elite attended the event.

In 1916, the theatre acquired a resident organization (Pavel Amirago's opera troupe) and began to function on a permanent basis. In 1920, it became a state theatre known as the Opera and Ballet Theatre. In 1925, the Azerbaijani Opera Troupe, the Russian Opera Troupe and the Drama Troupe united to become the official resident organization. In 1959, it received the status of an academic theatre. In 1985, the newly renovated theatre mysteriously burned down. In 1987, all the restoratory works were finished and the theatre reopened its doors. Azerbaijan State Opera Theare celebrates it's 100^th Anniversary in 2020, which is an oldest opera theatre in this region.