The Azerbaijan Soviet Socialist Republic (Azerbaijan SSR; Azerbaijani: Азәрбајҹан Совет Сосиалист Республикасы, Azərbaycan Sovet Sosialist Respublikası; Russian: Азербайджанская Советская Социалистическая Республика [АзССР], Azerbaydzhanskaya Sovetskaya Sotsialisticheskaya Respublika [AzSSR]), also referred to as Soviet Azerbaijan or simply known as Azerbaijan was one of the constituent republics of the Soviet Union.
Established on 28 April 1920 as the Azerbaijan SSR, from 12 March 1922 to 5 December 1936, it was part of the Transcausasian 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 Constitution of the Azerbaijan SSR ceased to exist in 1995, upon the adoption of the new Constitution of Azerbaijan.