Anti-communism is political and ideological opposition to communist beliefs, groups, and individuals. 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 expressed by several religious groups, and in art and literature. Anti-communism has been an element of many movements and different political positions across the political spectrum, including anarchism, centrism, conservatism, fascism, liberalism, nationalism, social democracy, socialism, leftism, and libertarianism, as well as broad 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 America and in Europe was promoted by conservatives, monarchists, fascists, liberals, and social democrats. Fascist governments rose to prominence as major opponents of communism in the 1930s. Liberal and social democrats in Germany formed the Iron Front to oppose communists, Nazi fascists, and revanchist conservative monarchists alike. In 1936, the Anti-Comintern Pact, initially between Nazi Germany and Imperial Japan, was formed as an anti-communist alliance. In Asia, Imperial Japan and the Kuomintang (Chinese Nationalist Party) were the leading anti-communist forces in this period.

By 1945, the communist Soviet Union was among major Allied nations fighting against the Axis powers in World War II (WII.) Shortly after the end of the war, 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 First Indochina 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 communist 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 the People's Republic of China and other communist states.

Since the split of the Communist parties from the socialist Second International to form the Marxist–Leninist Third International, social democrats have been critical of Communism for its anti-liberal nature. Examples of left-wing critics of Marxist–Leninist states and parties are Friedrich Ebert, Boris Souvarine, George Orwell, Bayard Rustin, Irving Howe, and Max Shachtman. The American Federation of Labor was always strongly anti-communist. The more left-wing Congress of Industrial Organizations purged its communists in 1947 and was staunchly anti-communist afterwards. In the United Kingdom, the Labour Party strenuously resisted Communist efforts to infiltrate its ranks and take control of locals in the 1930s. The Labour Party became anti-communist and UK Prime Minister Clement Attlee was a staunch supporter of NATO.

Despite anarchist communism being an anarchist school of thought, there are also anarchists who oppose communism. Anti-communist anarchists include anarcho-primitivists and other green anarchists, who critique communism for its need of industrialisation and its perceived authoritarianism.^{[better source needed]}

In The Communist Manifesto, Karl Marx and Friedrich Engels outlined some provisional short-term measures that could be steps towards communism. They noted that "these measures will, of course, be different in different countries. Nevertheless, in most advanced countries, the following will be pretty generally applicable." Ludwig von Mises described this as a "10-point plan" for the redistribution of land and production and argued that the initial and ongoing forms of redistribution constitute direct coercion. Neither Marx's 10-point plan nor the rest of the manifesto say anything about who has the right to carry out the plan. Milton Friedman argued that the absence of voluntary economic activity makes it too easy for repressive political leaders to grant themselves coercive powers. Friedman's view was also shared by Friedrich Hayek and John Maynard Keynes, both of whom believed that capitalism is vital for freedom to survive and thrive. Ayn Rand was strongly anti-communist. She argued that Communist leaders typically claim to work for the common good, but many or all of them were corrupt and totalitarian.