The 43rd Battalion was an Australian Army infantry unit that was originally formed during the First World War as part of the all-volunteer Australian Imperial Force. Raised in early 1916, the battalion subsequently fought in the trenches of the Western Front from late 1916 until the end of the war in November 1918. After the war, the 43rd was re-raised as a part-time unit in South Australia, serving until 1930 when it was merged with the 48th Battalion. During the Second World War, the 43rd was briefly re-raised between 1942 and 1944, but did not see action before it was disbanded. After the war, the 43rd and 48th were once again merged, existing until 1960 when they became part of the Royal South Australia Regiment.