42nd Battalion
- 42 Commando
- 42nd (East Lancashire) Infantry Division
- 42nd Battalion (Australia)
- 42nd Battalion (Royal Highlanders of Canada), CEF
- 42nd Battalion, CEF
- 42nd Battalion, Singapore Armoured Regiment
- 42nd Brigade (disambiguation)
- 42nd Division (disambiguation)
- 42nd Group (disambiguation)
- 42nd Regiment (disambiguation)
- 42nd Squadron (disambiguation)
- 42nd Virginia Cavalry Battalion
- Robin Hood Battalion