The Communist Party of Australia is founded in Sydney.

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. At its peak it was the largest communist party in the Anglophone countries on a population basis, and held industrial strength greater than the parties of "India, Latin America, and most of Western Europe".