The vice chairman of the Joint Chiefs of Staff (VJCS) is, by U.S. law, the second highest-ranking military officer in the United States Armed Forces, ranking just below the chairman of the Joint Chiefs of Staff. The vice chairman outranks all respective heads of each service branch, with the exception of the chairman, but does not have operational command authority over their service branches. The vice chairman assists the chairman in exercising their duties. In the absence of the chairman, the vice chairman presides over the meetings of the Joint Chiefs of Staff and performs all other duties prescribed under 10 U.S.C. § 153 and may also perform other duties that the president, the chairman, or the secretary of defense prescribes.

The United States Armed Forces are the military forces of the United States. The armed forces consist of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. All six armed services are among the eight uniformed services of the United States.