3rd Cavalry
- 3d Armored Cavalry Squadron (South Vietnam)
- 3rd (Ambala) Cavalry Brigade
- 3rd (Meerut) Cavalry Brigade
- 3rd Arkansas Cavalry Regiment (Confederate)
- 3rd Arkansas Cavalry Regiment (Union)
- 3rd Bengal Cavalry
- 3rd Bengal Light Cavalry
- 3rd Brigade Combat Team, 1st Cavalry Division (United States)
- 3rd Cavalry (India)
- 3rd Cavalry Brigade (Australia)
- 3rd Cavalry Brigade (Germany)
- 3rd Cavalry Brigade (Imperial Japanese Army)
- 3rd Cavalry Brigade (Poland)
- 3rd Cavalry Brigade (United Kingdom)
- 3rd Cavalry Division (German Empire)
- 3rd Cavalry Division (Reichswehr)
- 3rd Cavalry Division (United Kingdom)
- 3rd Cavalry Division (United States)
- 3rd Cavalry Division Amedeo Duca d'Aosta
- 3rd Cavalry Regiment (Australia)
- 3rd Cavalry Regiment (United States)
- 3rd Colorado Cavalry Regiment
- 3rd Kentucky Cavalry Regiment (Union)
- 3rd Madras Cavalry
- 3rd Michigan Volunteer Cavalry Regiment
- 3rd Ohio Cavalry
- 3rd Regiment Illinois Volunteer Cavalry
- 3rd Regiment Indiana Cavalry
- 3rd Regiment Iowa Volunteer Cavalry
- 3rd Virginia Cavalry
- 3rd West Virginia Volunteer Cavalry Regiment
- 3rd Wisconsin Volunteer Cavalry Regiment
- III Cavalry Corps (German Empire)
- III Cavalry Corps (Grande Armée)