40th Battalion may refer to:
40th Battalion (Australia), an infantry battalion 1916–1987 40th Battalion (Nova Scotia), CEF, a Canadian infantry battalion during World War I Sparrow Force (2/40th Australian Infantry Battalion), a unit of the Australian Army 40 Commando, a unit of the United Kingdom Royal Marine Corps
See also 40th Division (disambiguation) 40th Brigade (disambiguation) 40th Regiment (disambiguation) 40th Squadron (disambiguation)