Short for Master Chief Petty Officer.
The Master Chief Petty Officer is the ninth, and highest, enlisted rank in the U.S. Navy, just above
Senior Chief Petty Officer, and is a non-commissioned officer. They are referred to as Master Chief in most
circumstances.
Advancement to Master Chief Petty Officer is similar to that of Chief Petty Officer and Senior Chief Petty Officer. It carries requirements of time in service, superior evaluation scores, specialty examinations, and peer review. A Senior Chief Petty Officer can only advance if the existing master chiefs approve.
A Master Chief Petty Officer is purely administrative and is usually tied closely with the Commanding Officer, except possibly when the command is very large (e.g. an aircraft carrier). Their uniform reflects this administrative duty; becoming similar to that of an officer, albeit with different insignia than an officer.