II Field Force, Vietnam was a United States Army Corps-level command during the Vietnam War.

Activated on 15 March 1966, it became the largest corps command in Vietnam and one of the largest in Army history. II Field Force was assigned the lineage of the XXII Corps, a World War II corps in the European Theater of Operations. II Field Force was a component of U.S. Military Assistance Command Vietnam (MACV) and had its headquarters in Long Binh.

II Field Force's area of responsibility was III Corps Tactical Zone, later renamed Military Region 3, which comprised eleven provinces surrounding Saigon. This was designed to mimic the ARVN III Corps region. II Field Force controlled units participating in the 1968 Tet Offensive and the 1970 Cambodian Incursion.