The Azerbaijan Soviet Socialist Republic (Azerbaijani: Azərbaycan Sovet Sosialist Respublikası; Russian: Азербайджанская Советская Социалистическая Республика [АзССР] Azerbaydzhanskaya Sovetskaya Sotsialisticheskaya Respublika [AzSSR]), also known as the Azerbaijan SSR for short, was one of the republics that made up the former Soviet Union.
Established on April 28, 1920 as the Azerbaijan SSR. From March 12, 1922 to December 5, 1936, it was part of the Transcaucasian SFSR together with the Armenian SSR and the Georgian SSR. In December 1922, Transcaucasian SFSR became part of the newly established Soviet Union. The Constitution of Azerbaijan SSR was approved by the 9th Extraordinary All-Azerbaijani Congress of Soviets on March 14, 1937. On November 19, 1990, Azerbaijan SSR was renamed the "Republic of Azerbaijan," remaining in the USSR for another year before its independence in 1991.