State atheism is the incorporation of hard atheism or non-theism into political regimes. It may also refer to large-scale secularization attempts by governments. To some extent, it is a religion-state relationship that is usually ideologically linked to irreligion and the promotion of irreligion. State atheism may refer to a government's promotion of anti-clericalism, which opposes religious institutional power and influence in all aspects of public and political life, including the involvement of religion in the everyday life of the citizen. In some instances, religious symbols and public practices that were once held by religions were replaced with secularized versions of them. State atheism can also exist in a politically neutral fashion, in which case, it is considered non-secular.
The majority of communist states followed similar policies from 1917 onwards. The Soviet Union (1922–1991) had a long history of state atheism, whereby those who were seeking social success generally had to profess atheism and stay away from places of worship; this trend became especially militant during the middle of the Stalinist era, which lasted from 1929 to 1953. In Eastern Europe, countries like Belarus, Bulgaria, Estonia, Latvia, Russia, and Ukraine experienced strong state atheism policies. East Germany and Czechoslovakia also had similar policies. The Soviet Union attempted to suppress public religious expression over wide areas of its influence, including places such as Central Asia. Either currently or in their past, China, North Korea, Vietnam, Cambodia, and Cuba are or were officially atheist.
In contrast, a secular state officially purports to be neutral in matters of religion, it does not support religion nor does it support irreligion. In a review of 35 European states in 1980, 5 states were considered "secular" in the sense of religious neutrality, 9 considered "atheistic", and 21 states considered "religious".