First Army

• 1st Army (Austria-Hungary)
• 1st Army (France)
• 1st Army (German Empire)
• 1st Army (Kingdom of Yugoslavia)
• 1st Army (Russian Empire)
• 1st Army (Wehrmacht)
• 1st Brigade (disambiguation)
• 1st Division (disambiguation)
• 1st Group Army
• 1st Guards Tank Army (Russia)
• 1st Panzer Army
• 1st Parachute Army (Wehrmacht)
• 1st Red Banner Army
• 1st Regiment (disambiguation)
• 1st Shock Army
• First Allied Airborne Army
• First Army (Bulgaria)
• First Army (Greece)
• First Army (Hungary)
• First Army (Italy)
• First Army (Japan)
• First Army (Ottoman Empire)
• First Army (Romania)
• First Army (Serbia)
• First Army (Turkey)
• First Army (United Arab Republic)
• First Army (United Kingdom)
• First Australian Army
• First Canadian Army
• First Field Army
• First Polish Army (1920)
• First Polish Army (1944–1945)
• First United States Army
• I Corps (disambiguation)
• New 1st Army