The 12th Brigade was an infantry brigade of the Australian Army. Formed in 1912 as a Militia formation, it was later re-raised in 1916 as part of the all volunteer First Australian Imperial Force that was raised for overseas service during the First World War. The brigade was part of the 4th Division and fought on the Western Front until the end of the war in November 1918. During the inter-war years, the brigade was re-formed in Australia as a part-time unit; during the Second World War, it was mobilised for full-time service, but did not serve overseas, undertaking garrison duties in Australia until 1945 when it was used to raise Timor Force.

The Australian 4th Division was formed in the First World War during the expansion of the Australian Imperial Force (AIF) infantry brigades in February 1916. In addition to the experienced 4th Brigade were added the new 12th and 13th Brigades. From Egypt the division was sent to France, where it took part in the fighting on the Western Front during 1916–1918. After the war ended, the AIF was demobilised and the division was dissolved.