3rd Corps, Third Corps, III Corps, or 3rd Army Corps may refer to:
France
- 3rd Army Corps (France)
- III Cavalry Corps (Grande Armée), a cavalry unit of the Imperial French Army during the Napoleonic Wars
- III Corps (Grande Armée), a unit of the Imperial French Army during the Napoleonic Wars
Germany
- III Cavalry Corps (German Empire), a unit of the Imperial German Army
- III Corps (German Empire), a unit of the Imperial German Army
- III Reserve Corps (German Empire), a unit of the Imperial German Army
- III Royal Bavarian Corps, a unit of the Bavarian Army and the Imperial German Army
- III Army Corps (Wehrmacht), a unit in World War II
- III Corps (Bundeswehr)
- III Panzer Corps (Germany)
- III (Germanic) SS Panzer Corps
Russia and Soviet Union
- 3rd Army Corps (Russian Empire), a unit in World War I
- 3rd Mechanized Corps (Soviet Union)
- 3rd Rifle Corps, Soviet Union
- 3rd Army Corps (Russia), Russian Federation
United States
- III Corps (United States)
- III Corps (Union Army)
- Third Army Corps (Spanish–American War)
- Third Corps, Army of Northern Virginia
- Third Corps, Army of Tennessee
Others
- 3rd Army Corps (Armenia)
- 3rd Army Corps (Azerbaijan)
- III Corps (Australia)
- Finnish III Corps (Winter War)
- Finnish III Corps (Continuation War)
- III Army Corps (Greece)
- III Corps (India)
- 3rd Army Corps (Italy)
- III Corps (North Korea)
- III Corps (Ottoman Empire)
- III Corps (South Korea)
- III Corps (South Vietnam)
- 3rd Corps (Syria)
- 3rd Corps (Turkey)
- 3rd Army Corps (Ukraine)
- III Corps (United Kingdom)
- 3rd Corps (Vietnam People's Army)
See also
- List of military corps by number
- 3rd Army (disambiguation)
- 3rd Battalion (disambiguation)
- 3rd Brigade (disambiguation)
- 3rd Division (disambiguation)
- 3rd Regiment (disambiguation)
- 3 Squadron (disambiguation)