2nd Regiment
- 2/39 Evzone Regiment
- 2/6th Cavalry Commando Regiment (Australia)
- 2e régiment de chevau-légers lanciers de la Garde Impériale
- 2nd Air Defense Artillery Regiment
- 2nd Alabama Volunteer Infantry Regiment (African Descent)
- 2nd Albany County Militia Regiment
- 2nd Alpine Artillery Regiment
- 2nd Alpine Engineer Regiment
- 2nd Alpine Signal Regiment
- 2nd Alpini Regiment
- 2nd Armoured Regiment (Poland)
- 2nd Aviation Regiment (United States)
- 2nd Canadian Regiment
- 2nd Cavalry Regiment (Australia)
- 2nd Cavalry Regiment (United States)
- 2nd Connecticut Regiment
- 2nd East Anglian Regiment
- 2nd Field Artillery Regiment (United States)
- 2nd Field Artillery Regiment/Field Artillery Battery ParaCommando
- 2nd Field Regiment, Royal Canadian Artillery
- 2nd Foreign Engineer Regiment
- 2nd Foreign Infantry Regiment
- 2nd Foreign Parachute Regiment
- 2nd Georgia Regiment
- 2nd Guards Field Artillery
- 2nd Infantry (2nd Palmetto Regiment)
- 2nd Infantry Regiment (Lithuania)
- 2nd Infantry Regiment (South Korea)
- 2nd Infantry Regiment (United States)
- 2nd Iowa Regiment
- 2nd Kentucky Infantry Regiment (Confederate)
- 2nd Kentucky Infantry Regiment (Union)
- 2nd Lancers Regiment (Portugal)
- 2nd Legions' Infantry Regiment
- 2nd Maine Volunteer Infantry Regiment
- 2nd Marine Infantry Parachute Regiment
- 2nd Marine Regiment (United States)
- 2nd Maryland Infantry Regiment (Confederate)
- 2nd Maryland Infantry Regiment (disambiguation)
- 2nd Maryland Regiment
- 2nd Massachusetts Regiment
- 2nd Michigan Volunteer Cavalry Regiment
- 2nd Michigan Volunteer Infantry Regiment
- 2nd Minnesota Volunteer Cavalry Regiment
- 2nd Nebraska Cavalry
- 2nd New Hampshire Regiment
- 2nd New Hampshire Volunteer Regiment
- 2nd New Jersey Regiment
- 2nd New York Regiment
- 2nd New York Volunteer Infantry Regiment
- 2nd North Carolina Regiment
- 2nd Ohio Infantry
- 2nd Oregon Volunteer Infantry Regiment
- 2nd Pennsylvania Regiment
- 2nd Punjab Regiment
- 2nd Queen Victoria's Own Rajput Light Infantry
- 2nd Regiment Alabama Volunteer Cavalry (Confederate)
- 2nd Regiment Illinois Volunteer Cavalry
- 2nd Regiment Indiana Cavalry
- 2nd Regiment Iowa Volunteer Cavalry
- 2nd Regiment Kansas Volunteer Infantry (African Descent)
- 2nd Regiment Massachusetts Volunteer Heavy Artillery
- 2nd Regiment Massachusetts Volunteer Infantry
- 2nd Regiment South Carolina Volunteer Infantry (African Descent)
- 2nd Regiment Wisconsin Volunteer Cavalry
- 2nd Regiment of Cavalry, Massachusetts Volunteers
- 2nd Rhode Island Regiment
- 2nd Royal Tank Regiment
- 2nd Serres Regiment
- 2nd South Carolina Regiment
- 2nd Tangier Regiment
- 2nd Training Aviation Regiment
- 2nd United States Infantry Regiment (Civil War)
- 2nd United States Volunteer Sharpshooter Regiment
- 2nd Virginia Infantry
- 2nd Virginia Regiment
- 2nd Virginia Volunteer Infantry (1898)
- 2nd West Virginia Veteran Volunteer Infantry Regiment
- 2nd West Virginia Volunteer Cavalry Regiment
- 2nd West Virginia Volunteer Infantry Regiment
- 2nd Wisconsin Volunteer Infantry Regiment
- 2nd Yugoslav Assault Regiment
- 2nd/10th Medium Regiment, Royal Australian Artillery
- 2nd/14th Light Horse Regiment
- 2nd/4th Lancers Regiment
- 2nd/4th Regiment Mounted Rifles
- 64th (2nd Staffordshire) Regiment of Foot
- 65th (2nd Yorkshire, North Riding) Regiment of Foot
- Kingdom of Holland
- Nevers' 2nd Regiment Band
- Second Division (disambiguation)