Fifth Army may refer to:
Germany
- 5th Army (German Empire), a World War I field Army
- 5th Army (Wehrmacht), a World War II field army
- 5th Panzer Army
- 5th Army (GDR), a Warsaw Pact field army in the Cold War to be activated in case of a war with NATO
Russia/USSR
- 5th Army (Russian Empire)
- 5th Army (RSFSR)
- 5th Army (Soviet Union)
- 5th Combined Arms Army (Russian Federation)
Others
- 5th Army (Austria-Hungary)
- Fifth Army (Bulgaria)
- Fifth Army (Nationalist China), see 88th Division (National Revolutionary Army)
- Fifth Army (France)
- Fifth Army (Japan)
- Fifth Army (Ottoman Empire)
- Fifth Army (United Kingdom)
- Fifth United States Army
- Fifth Army (Italy)
- 5th Army (Kingdom of Yugoslavia)
- Special Frontier Force of India, during the Indo-Pakistani War of 1971