The 12th Battalion was an infantry battalion originally raised for the First Australian Imperial Force during the First World War. The battalion was recruited from Tasmania, South Australia and Western Australia and formed part of the 3rd Brigade, 1st Division. It served throughout the war, firstly during the Gallipoli Campaign and then on the Western Front. During the interwar years, the 12th Battalion was re-raised as a part-time military unit and during the Second World War undertook garrison duties in Australia, but did not see combat. Today its lineage is perpetuated by the 12th/40th Battalion, Royal Tasmania Regiment, a unit which continues to serve in the Australian Army Reserve.