The 15th Brigade was an infantry brigade of the Australian Army. Originally raised in 1912 as a Militia formation, the brigade was later re-raised in 1916 as part of the First Australian Imperial Force during World War I. The brigade took part in the fighting on the Western Front in France and Belgium during 1916–1918 before being disbanded in 1919. After this it was re-raised as a part-time unit of the Citizens Force in 1921 in Victoria. During World War II the brigade undertook defensive duties and training in Victoria and Queensland, before being deployed to New Guinea in 1943. Over the course of 1943 and 1944, it took part in the Salamaua–Lae, Markham–Ramu campaigns before returning to Australia in late 1944. In mid-1945, the brigade was committed to the Bougainville campaign, before being disbanded following the end of hostilities.