The Communist Party of Australia is founded in Sydney.

The Communist Party of Australia (CPA) was founded on 30 October 1920 in Sydney, inspired by the Russian Revolution of 1917 and the growing international communist movement. Its formation brought together socialist activists, militant trade unionists and members of the Industrial Workers of the World who believed capitalism should be replaced by a socialist society. The party became affiliated with the Communist International, an organisation established by the Soviet Union to promote communist revolutions around the world. During its early years, the CPA struggled to attract widespread support, competing with the Australian Labor Party for influence among working-class voters. However, the Great Depression of the 1930s provided opportunities for growth, as unemployment, poverty and industrial unrest encouraged some Australians to embrace radical political ideas. The party became increasingly active in trade unions, unemployment campaigns and protests against economic inequality.

During the 1930s and 1940s, the Communist Party of Australia expanded its influence within the Australian labour movement, particularly in industries such as mining, shipping, construction and waterfront employment. Its members played prominent roles in organising strikes and campaigning for improved wages and working conditions. The party also opposed fascism and supported the Republican cause during the Spanish Civil War. Following the outbreak of the Second World War in 1939, the CPA initially opposed Australia’s participation in what it regarded as an imperialist conflict, reflecting the Soviet Union’s non-aggression pact with Nazi Germany. The Australian government banned the party in June 1940, forcing it to operate underground. However, when Germany invaded the Soviet Union in June 1941, the communists became enthusiastic supporters of the Allied war effort. The ban was lifted in December 1942, and the party subsequently experienced its greatest period of popularity, reaching approximately 23,000 members during the mid-1940s.

The beginning of the Cold War in the late 1940s brought increasing hostility towards the Communist Party, as fears of Soviet expansion and communist infiltration spread throughout Australia. Prime Minister Robert Menzies, who returned to power in 1949, regarded the CPA as a threat to national security and introduced the Communist Party Dissolution Act in 1950, which sought to outlaw the organisation. However, the High Court of Australia declared the legislation unconstitutional in March 1951. Menzies subsequently held a national referendum on 22 September 1951, seeking constitutional powers to ban the party, but the proposal was narrowly defeated, with 50.56% of voters opposing it. Despite surviving these attempts to suppress it, the CPA experienced declining membership and influence throughout the 1950s. Revelations about Joseph Stalin’s repression, particularly following Nikita Khrushchev’s denunciation of Stalin in 1956, and the Soviet invasion of Hungary that same year caused considerable disillusionment among Australian communists. Many members resigned, while ideological disagreements increasingly divided the organisation.

During the 1960s and 1970s, the Communist Party of Australia gradually distanced itself from the Soviet Union and became increasingly involved in broader social movements, including opposition to the Vietnam War, women’s liberation, Aboriginal land rights and environmental protection. However, ideological divisions resulted in several important splits, including the formation of the Maoist Communist Party of Australia (Marxist-Leninist) in 1964 and the pro-Soviet Socialist Party of Australia in 1971. The original CPA increasingly embraced democratic socialism and the ideas of the New Left, abandoning much of its earlier commitment to Soviet-style communism. By the 1980s, declining membership, reduced trade union influence and changing international political circumstances had weakened the organisation considerably. The collapse of communist governments across Eastern Europe further undermined its political identity, and the original Communist Party of Australia formally dissolved in 1991. Although the Socialist Party of Australia adopted the Communist Party of Australia name in 1996, it remained a separate organisation from the original party. Despite never achieving significant electoral success, the original CPA left a lasting legacy in Australian political history through its influence on trade union activism, workers’ rights, cultural movements and campaigns for social reform.