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)

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)
• Third Army (Turkey)
• Third Army (United Kingdom)
  • Third Army (Home Forces), also in the United Kingdom
• Third Army (United States)