In the United States Army, Marine Corps, and Air Force, major is a field grade military officer rank above the rank of captain and below the rank of lieutenant colonel. It is equivalent to the naval rank of lieutenant commander in the other uniformed services. Although lieutenant commanders are considered junior officers by their respective services (Navy and Coast Guard), the rank of major is that of a senior officer in the United States Army, the United States Marine Corps, and the United States Air Force.

The pay grade for the rank of major is O-4. The insignia for the rank consists of a golden oak leaf, with slight stylized differences between the Army/Air Force version and the Marine Corps version. Promotion to major is governed by the Department of Defense policies derived from the Defense Officer Personnel Management Act of 1980.