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)