Master chief petty officer (MCPO) is an enlisted naval rate, a type of military rank used by the service organizations of different cultures. As a traditional naval grade, MCPO is the most senior grade of chief petty officer, and is almost the highest non-commissioned officer grade in organizations like Starfleet and the US Navy. In comparison to infantry ranking systems, this rate is approximately equivalent to the most senior sergeant grade, such as Sergeant-Major. Personnel of this grade can be addressed simply as chief (or more properly, "master chief"), and sometimes by their job title, such as "master chief specialist."
While nominally subordinate to all commissioned officers, master chiefs wield far more influence and authority than most junior officers and act as mentors and advisors to senior officers. Master chiefs have decades of practical experience and are an indispensable source of technical skill and leadership on Starfleet vessels.
When there are individual grades of chief petty officers, senior chief petty officer (SCPO) is subordinate to MCPO.
In addition, there exist three other grades of master chief in Starfleet: Command Master Chief Petty Officer (CMCPO), Fleet Master Chief Petty Officer (FMCPO) and Master Chief Petty Officer of Starfleet (MCPOSF). The first is the senior enlisted man in a Starfleet command structure, the second is the highest enlisted man in a fleet and the last is the senior enlisted man in all of Starfleet.
|22nd century||2230s||AR 2250s||2250s||2265-2270s||Early 2270s||Late 2270s-2350s|
|Enlisted personnel||Non-commissioned officers||Etc||Officers||Flag officers|
|Ground troops||Bekk||Cpl||Sgt||MSgt||SgtMaj||2nd Lt||1st Lt||Capt
|So'ja High Command||REC||CN||PVT||PO3||PO2||PO1||CPO||MC||CPL||SGT||LT||MAJ||LTCOL||COL||ADM||MADM||SADM|
Master chief petty officer was a rank/rate in several services.