Byelorussian Soviet Socialist Republic

The Byelorussian Soviet Socialist Republic (BSSR, or Byelorussian SSR; Belarusian: Беларуская Савецкая Сацыялістычная Рэспубліка, romanized: Byelaruskaya Savyetskaya Satsyyalistychnaya Respublika; Russian: Белорусская Советская Социалистическая Республика, romanized: Byelorusskaya Sovetskaya Sotsialisticheskaya Respublika), also known as Byelorussia, Soviet Belarus, or simply Belarus, was a republic of the Soviet Union (USSR). It existed between 1920 and 1991 as one of fifteen constituent republics of the USSR, with its own legislation from 1990 to 1991. The republic was ruled by the Communist Party of Byelorussia and was also referred to as Soviet Byelorussia or Soviet Belarus by a number of historians. Other names for Byelorussia included White Russia or White Russian Soviet Socialist Republic and Belorussian Soviet Socialist Republic.

To the west it bordered Poland. Within the Soviet Union, it bordered the Lithuanian SSR and the Latvian SSR to the north, the Russian SFSR to the east, and the Ukrainian SSR to the south.

The Socialist Soviet Republic of Byelorussia (SSRB) was declared by the Bolsheviks on 1 January 1919 following the declaration of independence by the Belarusian Democratic Republic in March 1918. In 1922, the BSSR was one of the four founding members of the Soviet Union, together with the Ukrainian SSR, the Transcaucasian SFSR, and the Russian Soviet Federative Socialist Republic (RSFSR). Byelorussia was one of several Soviet republics occupied by Nazi Germany during World War II.

Towards the final years of the Soviet Union's existence, the Supreme Soviet of Byelorussian SSR adopted the Declaration of State Sovereignty in 1990. On 25 August 1991, the Byelorussian SSR declared independence, and on 19 September it was renamed the Republic of Belarus. The Soviet Union was dissolved on 26 December 1991.