The USSR anti-religious campaign (1921–1928) was a campaign of anti-religious persecution against churches and Christian believers by the Soviet government following the initial anti-religious campaign during the Russian Civil War. The elimination of all religion and its replacement with scientific materialism was a fundamental ideological goal of the state. To this end, the state began offering secular education to believers, intending to reduce the prevalence of superstition. It was never made illegal to be a believer or to have religion, and so the activities of this campaign were often veiled under other pretexts that the state invoked or invented in order to justify its activities.

Following the October Revolution of 1917, the Bolshevik seizure of power led to the Russian Civil War which continued until 1922. The victory of the Bolshevik Red Army enabled them to set up the Union of Soviet Socialist Republics (USSR). Throughout the civil war various religions, secularists and anti-clericalists of the Bolsheviks played a key role in the military and social struggles which occurred during the war.