, plural Bolsheviks, or Bolsheviki, member of a wing of the Russian Social-Democratic Workers’ Party, which, led by Lenin, seized control of the government in Russia (October 1917) and became the dominant political power. The group originated at the party’s second congress (1903) when Lenin’s followers, insisting that party membership be restricted to professional revolutionaries, won a temporary majority on the party’s central committee and on the editorial board of its newspaper Iskra. They assumed the name Bolsheviks and dubbed their opponents the Mensheviks (“Those of the Minority”).