The 25th Battalion was an infantry unit of the Australian Army. Raised in early 1915 as part of the Australian Imperial Force during the First World War, the battalion fought at Gallipoli and in the trenches along the Western Front, before being disbanded in early 1919. In mid-1921, it was re-formed as a part-time unit based in the state of Queensland. Throughout the 1930s, the battalion was merged briefly with the 49th Battalion as a result of manpower shortages, but was later re-raised in its own right. During the Second World War, the 25th deployed to New Guinea where they fought the Battle of Milne Bay in August and September 1942. Later in the war, the 25th took part in the Bougainville Campaign. During the post-war period, the 25th Battalion became part of the Royal Queensland Regiment, variously forming battalion or company-sized elements, before being merged with the 49th Battalion to form the 25th/49th Battalion, Royal Queensland Regiment.

The First Australian Imperial Force was the main expeditionary force of the Australian Army during the First World War. It was formed as the Australian Imperial Force (AIF) following Britain's declaration of war on Germany on 15 August 1914, with an initial strength of one infantry division and one light horse brigade. The infantry division subsequently fought at Gallipoli between April and December 1915, with a newly raised second division, as well as three light horse brigades, reinforcing the committed units.