III Corps was an Australian Army unit during World War II. It was responsible for the defence of Western Australia in 1942–1944. The corps was formed in April 1942 from Western Command, which had been established in October 1939. Throughout the war, the formation's size expanded and contracted as available manpower, and the strategic situation, dictated. At its height, the corps consisted of two infantry divisions and one armoured division, which were deployed to defend against a Japanese invasion threat, which ultimately never eventuated. The corps ceased to exist in June 1944 when it was converted back into Western Command, which remained until the end of the war in 1945.