The Communist Party of the Soviet Union was the Union of Soviet Socialist Republics' ruling party.
The Communist Party of the Soviet Union , abbreviated in English as CPSU , was the founding and ruling political party of the Union of Soviet Socialist Republics ( USSR or Soviet Union ) . The Soviet Union ( [ Сове́тский Сою́з , r = Sovetskiy Soyuz ] [ sɐ ` vʲetskʲɪj sɐˈjʉs ] ) , officially the Union of Soviet Socialist Republics ( USSR ; Сою́з Сове́тских Социалисти́ческих Респу́блик , [ sɐˈjus sɐˈvʲɛtskʲɪx sətsɨəlʲɪsˈtʲitɕɪskʲɪx rʲɪˈspublʲɪk ] ) , also known unofficially as Russia ( [ Росси́я , Rossiya , rɐˈsʲijə ] ) , was a socialist state in Eurasia that existed from 1922 to 1991 .