Third Army may refer to:
Germany
- 3rd Army (German Empire), a World War I field Army
- 3rd Army (Wehrmacht), a World War II field army
- 3rd Panzer Army
Russia and Soviet Union
- 3rd Army (Russian Empire)
- 3rd Army (RSFSR)
- 3rd Army (Soviet Union)
- 3rd Combined Arms Army
Others
- 3rd Army (Austria-Hungary)
- Third Army (Bulgaria)
- 3rd Army (France)
- Third Army (Egypt)
- Third Army (Hungary)
- Third Army (Italy)
- Third Army (Japan)
- Third Army (Ottoman Empire)
- Third Army (Romania)
- Third Army (Serbia)
- 3rd Army (South Korea)
- Third Army (Turkey)
- Third Army (United Kingdom)
- Third Army (Home Forces), also in the United Kingdom
- Third Army (United States)
See also
- 3rd Army Corps (disambiguation)
- 3rd Battalion (disambiguation)
- 3rd Brigade (disambiguation)
- 3rd Division (disambiguation)
- 3rd Regiment (disambiguation)
- 3rd Squadron (disambiguation)