The Eighth Army is a U.S. field army which commands all United States Army forces in South Korea. It is headquartered at the Camp Humphreys in the Anjeong-ri of Pyeongtaek, South Korea. Eighth Army relocated its headquarters from Yongsan to Camp Humphreys in the summer of 2017. It is the only field army in the U.S. Army. It is responsible to United States Forces Korea and United States Army, Pacific.

The United States Forces Korea (USFK) is a sub-unified command of U.S. Indo-Pacific Command (USINDOPACOM). USFK is the joint headquarters for U.S. combat-ready fighting forces and components under the ROK/US Combined Forces Command (CFC) – a supreme command for all of the South Korean and U.S. ground, air, sea and special operations component commands. Major USFK elements include U.S. Eighth Army (EUSA), U.S. Air Forces Korea, U.S. Naval Forces Korea (CNFK), U.S. Marine Forces Korea (MARFORK) and U.S. Special Operations Command Korea (SOCKOR). It was established on July 1, 1957.