The Armenian Soviet Socialist Republic (Armenian: Հայկական Սովետական Սոցիալիստական Հանրապետություն Haykakan Sovetakan Soc’ialistakan Hanrapetut’yun; Russian: Армя́нская Сове́тская Социалисти́ческая Респу́блика Armjanskaja Sovetskaja Sotsialističeskaja Respublika), also known as the Armenian SSR or Soviet Armenia for short, was one of the fifteen republics that made up the Soviet Union in December 1922. It was established in December 1920, when the Soviets took over control of the short-lived Democratic Republic of Armenia and lasted until 1991. It is sometimes called the Second Republic of Armenia, following the Democratic Republic of Armenia's demise (which was also known as the First Republic of Armenia).

As part of the Soviet Union, the Armenian SSR transformed from a largely agricultural hinterland to an important industrial production center. On August 23, 1990, it was renamed the Republic of Armenia, but remained in the Soviet Union until its official proclamation of independence on 21 September 1991. After the dissolution of the Soviet Union, the state of the post-Union Republic of Armenia existed until the adoption of the new constitution in 1995.

The Republics of the Soviet Union or the Union Republics (Russian: союзные республики, soyuznye respubliki) of the Soviet Union were ethnically-based administrative units that were subordinated directly to the Government of the Soviet Union. The Soviet Union was a highly centralized state.

According to the Article 76 of the Soviet Constitution, the sovereign Soviet socialist states united to become the Union of Soviet Socialist Republics. Article 81 of the Constitution stated that "the sovereign rights of Union Republics shall be safeguarded by the USSR".

In the final decades of its existence, the Soviet Union officially consisted of fifteen Soviet Socialist Republics (SSR). All of them were considered to be Soviet socialist republics (SSR), and all of them, with the exception of the Russian SFSR (until 1990), had their own Communist parties, part of the Communist Party of the Soviet Union.

Outside the territory of the Russian SFSR, the republics were constituted mostly in lands that had formerly belonged to the Russian Monarchy and had been acquired by it between the 1700 Great Northern War and the Anglo-Russian Convention of 1907.

A socialist state (or socialist republic) generally refers to any state constitutionally dedicated to the construction of a socialist society. It is closely related to the political strategy of "state socialism", a set of ideologies and policies that believe a socialist economy can be established through government policies. Alternatively, the term Worker's state is used to distinguish between a state where the working-class controls the machinery of government but has not established a socialist economy. These concepts are distinguished from a socialist government, which generally refers to a liberal democratic state presided over by an elected majority socialist party that is not, or does not necessarily have to be, pursuing the development of socialism; the state apparatus is not constitutionally bound to an eventual transition to socialism.

Non-statist socialists such as anarcho-socialists, libertarian socialists and council communists reject the concept of a "socialist state" altogether, believing that the modern state is a byproduct of capitalism and cannot be used, or is not required, to establish a socialist system. They reason that a socialist state is antithetical to socialism, and that socialism will emerge spontaneously from the grass-roots level in an evolutionary manner, developing its own unique political and economic institutions for a highly organized stateless society.