The 2/9th Battalion was an infantry battalion of the Australian Army during World War II. Raised in Queensland as part of the Second Australian Imperial Force (2nd AIF) shortly after the outbreak of the war, it served as part of the 18th Brigade and over the course of the war it was attached to the 6th, 9th and finally the 7th Division. It served in the United Kingdom in 1940, before taking part in the Siege of Tobruk and then the Syria-Lebanon campaign in 1941. In 1942 it was brought back to Australia where it took part in the New Guinea campaign throughout 1942–44. Its final involvement in the war was the Borneo campaign in 1945. It was disbanded shortly after the war in early 1946.