The Armenian Soviet Socialist Republic (Հայկական Սովետական Սոցիալիստական Հանրապետություն Haykakan Sovetakan Sotsialistakan Hanrapetutyun; Армянская Советская Социалистическая Республика Armyanskaya Sovetskaya Sotsialisticheskaya Respublika), also known as the Armenian SSR for short, was one of the republics that made up the former Soviet Union. It came into being when the Communist Party of Armenia proclaimed control of Armenia on November 29, 1920. On December 1, 1920, Prime Minister Simon Vratsian ceded control of the country. It later changed its name to the Armenian Soviet Socialist Republic. The period is sometimes known as the Second Republic of Armenia, which followed the short lived Democratic Republic of Armenia (also known as the First Republic of Armenia).

From 1828 to the October Revolution in 1917, Armenia was part of the then Russian Empire and confined to the borders of the Erivan Governorate. By Article 4 of the Treaty of Turkmenchay, the Erivan khanate (most of present-day central Armenia), which was a part of Persia was annexed by Russia in 1828.

After the October Revolution, Bolshevik leader Vladimir Lenin's government announced that minorities in the empire could pursue a course of self-determination. Following the collapse of the empire, Armenia, Azerbaijan and Georgia, declared themselves independent from Russian rule and each established their respective republics. After suffering numerous casualties under Ottoman rule during the Armenian Genocide and the subsequent Turkish-Armenian War, the historic Armenian area in the Ottoman Empire was overrun with despair and devastation. When the Democratic Republic of Armenia was invaded by the Bolsheviks in 1920, it was declared a Soviet republic.

Under Soviet rule, the Armenian SSR transformed from a largely agricultural hinterland to an important industrial production center. On August 23, 1990, it was renamed into Republic of Armenia, but remained in the Soviet Union until its official proclamation of independence in 1991.