State atheism is a popular term used for a government that is either antireligious, antitheistic or promotes atheism. In contrast, a secular state purports to be officially neutral in matters of religion, supporting neither religion nor irreligion. State atheism may refer to a government's 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.
State promotion of atheism as a public norm first came to prominence in Revolutionary France (1789–1799).Revolutionary Mexico followed similar policies from 1917, as did Marxist–Leninist states. The Russian Soviet Federative Socialist Republic (1917–1991) and the Soviet Union (1922–1991) had a long history of state atheism, whereby those seeking social success generally had to profess atheism and to stay away from houses of worship; this trend became especially militant during the middle Stalinist era from 1929 to 1939. The Soviet Union attempted to suppress public religious expression over wide areas of its influence, including places such as central Asia.
The United States and other secular states have used international treaties like the Universal Declaration of Human Rights to campaign for freedom of religion within politically repressive governments.