18th Brigade
- 18 Squadron (disambiguation)
- 18th (Croatian) Eastern Bosnian Brigade
- 18th Army (disambiguation)
- 18th Aviation Brigade (United States)
- 18th Battalion (disambiguation)
- 18th Brigade (Australia)
- 18th Division (disambiguation)
- 18th Engineer Brigade (United States)
- 18th Fires Brigade (United States)
- 18th Infantry Brigade (United Kingdom)
- 18th Military Police Brigade (United States)
- 18th Mounted Brigade (United Kingdom)
- 18th Regiment (disambiguation)
- XVIII Brigade, Royal Horse Artillery (T.F.)
- XVIII Corps (disambiguation)