The Bolsheviks, originally also Bolshevists or Bolsheviki (; derived from большинство bol'shinstvo, "majority", literally meaning "one of the majority") were a faction of the Marxist Russian Social Democratic Labour Party (RSDLP) which split apart from the Menshevik faction at the Second Party Congress in 1903. The RSDLP was revolutionary socialist political party formed in 1898 in Minsk to unite the various revolutionary organisations of the Russian Empire into one 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). The CPSU was the sole governing party of the Soviet Union until 1990 when the Supreme Soviet annulled the law which granted the CPSU a monopoly over the political system. The party was founded in 1912 by the Bolsheviks (the majority faction of the Russian Social Democratic Labour Party), a revolutionary group led by Vladimir Lenin which seized power in the aftermath of the October Revolution of 1917. The party was dissolved on 29 August 1991 soon after a failed coup d'état.