Master Chief Petty Officer of the Navy is the highest enlisted rank of the UNSC Navy. It is directly above Fleet/Force Master Chief Petty Officer. Warrant Officers are higher in rank, but MCPON is a more respectable (and harder to attain) position. It is equal in rank to Sergeant Major of the Marine Corps, Sergeant Major of the Army, and Chief Master Sergeant of the Air Force. In informal settings, Master Chief Petty Officers are typically called "Master Chief" or simply "Chief".
Master Chief Petty Officer of the Navy is selected by the Navy Chief of Staff. The MCPON is the senior enlisted member in the Navy, with a 3-star protocol equivalency. The MCPON represents the entire Navy enlisted force, and speaks on behalf of the enlisted members of the service to Navy and UNSCDF senior leadership.