Who is most important in the Marine Corps chain of command?

As in all branches of the military, the most important person in the chain of command of the U.S. Marine Corps is the President of the United States. As commander-in-chief, the president has ultimate authority over the nation's armed services.

Operationally, the command structure revolves around the commandant of the Marines Corps. The commandant is responsible for all matters concerning the Marines and advising senior political leaders such as the President and National Security Council. The Marines Corps commandant reports to the Secretary of the Navy. As of 2015, a total of 37 men have served as commandant of the Marine Corps.