Anti-communism refers to opposition to communism. Historically, the word "communism" has been used to refer to several types of communal social organization and their supporters, but, since the mid-19th century, the dominant school of communism in the world has been Marxism. Marxist communism drew far more supporters and opponents than any other form of communism. As such, the term anti-communism is most often employed to refer to opposition to Marxist communism. . The country best known for always being an opponent of communism is the United States , and maybe some of it's long-time allies like the United Kingdom , Canada France and Australia . Some wars and clashes betweens supporters and opposers of communism include the Vietnam War , the Korean War and the Bay of Pigs invasion . The 1980s Fall of Communism and the 1991 Collapse of the Soviet Union were seen as big victories for the opposers of communism .

Marxism, and the form of communism associated with it, rose to prominence in the 20th century. Organized anti-Communism developed in reaction to the growing popularity of the communist movement, and took on many forms as the 20th century unfolded. Conservative monarchists in Europe fought against the first wave of communist revolutions from 1917 to 1922. Fascism and Nazism were based on a violent brand of anti-communism, they incited fear of a communist revolution in order to gain political power, and they aimed to destroy communism in World War II. Nationalists fought against communists in numerous civil wars across the globe. Liberalism shaped much of the anti-communist foreign policy of the Western powers, and dominated anti-communist intellectual thought in the second half of the 20th century.

Following the October Revolution in Russia, Marxist communism became largely associated with the Soviet Union in the public imagination (though there were many Marxists and communists who did not support the Soviet Union and its policies). As a result, anti-communism and opposition to the Soviet Union became almost indistinguishable, especially in terms of foreign policy. Anti-communism was an important element in the foreign policy of the Axis powers during the 1930s and the United States during the Cold War.