Anti-communism is opposition to communism. Organized anti-communism developed in reaction to the rise of communism, especially after the 1917 October Revolution in Russia and reaching global dimensions during the Cold War.

Most^{[citation needed]} anti-communists reject^[who?] the concept of historical materialism, which is a central idea in Marxism. Anti-communists reject the Marxist belief that capitalism will be followed by socialism and communism, just as feudalism was followed by capitalism. Anti-communists question the validity of the Marxist claim that the socialist state will "wither away" when it becomes unnecessary in a true communist society.

Anti-communists argue that the repression in the early years of Bolshevik rule, while not as extreme as that during Joseph Stalin's rule, was still severe by reasonable standards, citing examples such as Felix Dzerzhinsky's secret police, which eliminated numerous political opponents by extrajudicial executions, and the brutal crushing of the Kronstadt rebellion and Tambov rebellion. Some anti-communists refer to both Communism and fascism as totalitarianism, seeing similarity between the actions of communist and fascist governments. Historian Robert Conquest has argued that Communism was responsible for tens of millions of deaths during the 20th century.