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 formed part of the 18th Brigade and over the course of the war it was attached to the 6th, 9th and 7th Divisions due to several re-organisations. It served in the United Kingdom in 1940, forming part of a small Australian garrison sent there to help defend against a possible German invasion, before being transferred to North Africa where it took part in the Siege of Tobruk and then undertook garrison duties in Syria following the Syria–Lebanon campaign in 1941.
In early 1942, the 2/9th was brought back to Australia where it was re-organised for jungle warfare and took part in the New Guinea campaign. Throughout 1942–1944, the battalion was committed twice to the fighting against the Japanese in New Guinea. In 1942–1943, the 2/9th fought actions at Milne Bay and Buna–Gona befo