U.S. MARINE CORPS
The smallest of the U.S. armed forces in the Department of Defense, the U.S. Marine Corps (USMC) is the branch of the U.S. military responsible for providing power projection from the sea, utilizing the mobility of the U.S. Navy to rapidly deliver combined-arms task forces to global crises. The Marine Corps operates alongside the U.S. Navy under the U.S. Department of the Navy.
Headquarters, U.S. Marine Corps (HQMC), located in Arlington, Virginia, is comprised of the Commandant of the Marine Corps (CMC) and related staff agencies that advise and assist the CMC in performing responsibilities assigned by higher authority. The CMC, who reports directly to the Secretary of the Navy (SECNAV), is responsible for the total performance of the Marine Corps, and includes such efforts as administration, discipline, internal organization, training requirements, efficiency, and service readiness. HQMC’s function, composition and general duties are defined in the U.S. Code, Title 10, Subtitle C, Part 1, Chapter 506. 
HQMC Organizational Chart
Source: USMC 
An interactive organizational chart for HQMC is available here
Updated by Kristin Stiner, March 2020