21st Division

21st Division  or 21st Infantry Division may refer to:

Infantry divisions

 * 21st Infantry Division (France)
 * 21st Division (German Empire)
 * 21st Reserve Division (German Empire)
 * 21st Infantry Division (Wehrmacht)
 * 21st Waffen Mountain Division of the SS Skanderbeg, Germany
 * 21st Infantry Division (India)
 * 21st Infantry Division Granatieri di Sardegna, Kingdom of Italy
 * 21st Infantry Division (India)
 * 21st Division (Imperial Japanese Army)
 * 21st Mountain Infantry Division (Poland)
 * 21st Division (South Vietnam)
 * 21st Division (Spain)
 * 21st Division (United Kingdom)
 * 21st Infantry Division (Iran)
 * 21st Division (People's Republic of China)

Cavalry divisions

 * 21st Cavalry Division (United States)

Armoured divisions

 * 21st Panzer Division (Wehrmacht), Germany

Aviation divisions

 * 21st Air Division (United States)