First Army

First Army may refer to:

China

 * New 1st Army, Republic of China
 * First Field Army, a Chinese Communist Party unit in the Chinese Civil War
 * 1st Group Army, People's Republic of China

Germany

 * 1st Army (German Empire), a World War I field Army
 * 1st Army (Wehrmacht), a World War II field army
 * 1st Panzer Army
 * 1st Parachute Army (Wehrmacht)

Russia and the Soviet Union

 * First Western Army
 * 1st Army (Russian Empire)
 * 1st Red Banner Army
 * 1st Shock Army
 * 1st Guards Tank Army (Russia)

Others

 * First Allied Airborne Army
 * First Australian Army
 * 1st Army (Austria-Hungary)
 * First Army (United Kingdom)
 * First Army (Bulgaria)
 * First Canadian Army
 * 1st Army (France)
 * First Army (Greece)
 * First Army (Hungary)
 * First Army (Italy)
 * First Army (Japan)
 * First Army (Ottoman Empire)
 * First Polish Army (1920)
 * First Polish Army (1944–1945)
 * First Army (Romania)
 * First Army (Serbia)
 * First Army (Turkey)
 * First Army (United Arab Republic)
 * First United States Army
 * 1st Army (Kingdom of Yugoslavia)