In military terms, 121st Division or 121st Infantry Division may refer to:
121st Infantry Division (German Empire) 121st Infantry Division (Wehrmacht), German unit in World War II 121st Division (Imperial Japanese Army) 121st Motor Rifle Division, Russia 121st Rifle Division, Soviet Union 121st Guards Rifle Division, Soviet Union
See also List of military divisions by number 121st Brigade (disambiguation) 121st Regiment (disambiguation) 121st Battalion (disambiguation) 121st Squadron (disambiguation) 121st (disambiguation)