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