Anti-communism is political and ideological opposition to communism. Organized anti-communism developed after the 1917 October Revolution in Russia and it reached global dimensions during the Cold War, when the United States and the Soviet Union engaged in an intense rivalry. Anti-communism has been an element of movements which hold many different political positions, including conservatism, fascism, liberalism, nationalism, social democracy, anarchism, libertarianism, and leftism. Anti-communism has also been expressed in philosophy, by several religious groups, and in literature. Some well-known proponents of anti-communism have been former communists. Anti-communism has also been prominent among movements resisting Communist governance.

The first organization which was specifically dedicated to opposing communism was the Russian White movement which fought in the Russian Civil War starting in 1918 against the recently established Bolshevik government. The White movement was militarily supported by several allied foreign governments which represented the first instance of anti-communism as a government policy. Nevertheless, the Red Army defeated the White movement and the Soviet Union was created in 1922. During the existence of the Soviet Union, anti-communism became an important feature of many different political movements and governments across the world.

In the United States, anti-communism came to prominence during the First Red Scare of 1919–1920. During the 1920s and 1930s, opposition to communism in Europe was promoted by conservatives, fascists, liberals, and social democrats. Fascist governments rose to prominence as major opponents of communism in the 1930s. In 1936, the Anti Comintern Pact, initially between Nazi Germany and the Empire of Japan, was formed as an anti-communist alliance.[1] In Asia, the Empire of Japan and the Kuomintang (the Chinese Nationalist Party) were the leading anti-communist forces in this period.

During World War II, the communist Soviet Union was among major Allied nations fighting the Axis Powers.[2] Shortly after the end of World War II, rivalry between the Marxist–Leninist Soviet Union and liberal-capitalist United States resulted in the Cold War. During this period, the United States government played a leading role in supporting global anti-communism as part of its containment policy. Military conflicts between Communists and anti-Communists occurred in various parts of the world, including during the Chinese Civil War, the Korean War, the Malayan Emergency, the Vietnam War, the Soviet–Afghan War and Operation Condor. NATO was founded as an anti-communist military alliance in 1949, and continued throughout the Cold War.

After the Revolutions of 1989 and the dissolution of the Soviet Union in 1991, most of the world's Marxist–Leninist governments were overthrown, and the Cold War ended. Nevertheless, anti-communism remains an important intellectual element of many contemporary political movements. Organized anti-communist movements remain in opposition to People's Republic of China and other Communist nations.