The Communist Party of Australia (CPA), known as the Australian Communist Party (ACP) from 1944 to 1951, was an Australian communist party founded in 1920. The party existed until roughly 1991, with its membership and influence having been in a steady decline since its peak in 1945. Like most communist parties in the West, the party was heavily involved in the labour movement and the trade unions. Its membership, popularity and influence grew significantly during most of the interwar period before reaching its climax in 1945, where the party achieved a membership of slightly above 22,000 members. Although the party did not achieve a federal MP, Fred Paterson was elected to the Parliament of Queensland at the 1944 state election. He won re-election in 1947 before the seat was abolished. The party also held office in over a dozen local government areas across New South Wales and Queensland.

The Australian labour movement began in the early 19th century and since the late 19th century has included industrial and political wings. Trade unions in Australia may be organised on the basis of craft unionism, general unionism, or industrial unionism. Almost all unions in Australia are affiliated with the Australian Council of Trade Unions (ACTU), many of which have undergone a significant process of amalgamations, especially in the late 1980s and early 1990s. The leadership and membership of unions hold and have at other times held a wide range of political views, including socialist, democratic and right-wing views.