18th Division or 18th Infantry Division may refer to:
Infantry divisions
- 18th Infantry Division (France)
- 18th Infantry Division (Wehrmacht), Germany
- 18th Division (German Empire)
- 18th Reserve Division (German Empire)
- 18th Infantry Division (Greece)
- 18th Division (Imperial Japanese Army)
- 18th Indian Division, a British Indian Army unit during World War I
- 18th Division (North Korea)
- 18th Infantry Division (Poland)
- 18th Division (South Vietnam)
- 18th Guards Motor Rifle Division, Russia
- 18th Rifle Division (Soviet Union)
- 18th (Eastern) Division, a United Kingdom division in World War I
- 18th Infantry Division (United Kingdom), a World War II division
- 39th Infantry Division (United States), briefly designated the 18th Division during 1917
- 18th Infantry Division Messina, an Italian unit in World War II
Cavalry divisions
- 18th Cavalry Division (Soviet Union)
Armoured divisions
- 18th Panzer Division (Wehrmacht), Germany
- 18th Tank Division (Soviet Union), part of the 7th Mechanized Corps in World War II
- 18th Armoured Division (Syria)
Artillery divisions
- 18th Artillery Division (Wehrmacht), Germany
- 18th Machine Gun Artillery Division, Soviet Union and Russia
- 18th Artillery Division (Soviet Union), part of the 42nd Army in World War II
Aviation divisions
- 18th Strategic Aerospace Division, United States