The Azerbaijan Soviet Socialist Republic (Azərbaycan Sovet Sosialist Respublikası; , Azerbaydzhanskaya Sovetskaya Sotsialisticheskaya Respublika [AzSSR] ), also known as the Azerbaijan SSR or Soviet Azerbaijan, was one of the republics that made up the former Soviet Union.
Established on 28 April 1920 as the Azerbaijan SSR, from 12 March 1922 to 5 December 1936, it was part of the Transcaucasian SFSR together with the Armenian SSR and the Georgian SSR. In December 1922, the 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 14 March 1937. On 19 November 1990, Azerbaijan SSR was renamed the "Republic of Azerbaijan," remaining in the USSR for another year before its independence in 1991. The state of the Azerbaijan SSR ceased to exist in 1995, upon the adoption of the new Constitution of Azerbaijan.