4th Regiment
- 1st Battalion, 258th Field Artillery (United States)
- 4th Air Defense Artillery Regiment
- 4th Archipelago Regiment
- 4th Cavalry Regiment (United States)
- 4th Combat Engineer Regiment (Australia)
- 4th Continental Artillery Regiment
- 4th Field Artillery Regiment
- 4th Infantry Regiment (France)
- 4th Infantry Regiment (Lithuania)
- 4th Infantry Regiment (United States)
- 4th Light Horse Regiment (Australia)
- 4th Lithuanian Vanguard Regiment
- 4th Marine Regiment (United States)
- 4th Mountain Artillery Regiment (Italy)
- 4th Regiment Royal Artillery
- 4th Regiment of Line Infantry
- 4th Regiment, Royal Australian Artillery
- 4th United States Colored Infantry Regiment
- Congress Poland
- King's Own Royal Regiment (Lancaster)