The Communist Party of the Soviet Union was the founding member of the Union of Soviet Socialist Republics.
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 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 .