In military terms, 91st Division or 91st Infantry Division may refer to:
Infantry divisions 91st Motorized Infantry Division, People's Republic of China 91st Infantry Division (German Empire) 91st Infantry Division (Wehrmacht), Germany 91st Division (Israel) 91st Division (Imperial Japanese Army) 91st Division (Philippines)
91st Guards Rifle Division, Soviet Union 91st Motor Rifle Division, Soviet Union 91st Rifle Division, Soviet Union 91st Division (United States)
Aviation divisions 91st Air Division, United States
See also 91st Division Monument List of military divisions by number 91st Brigade (disambiguation) 91st Regiment (disambiguation)