Master Gunnery Sergeant (MGySgt) is the ninth and highest enlisted rank (along with the grade-equivalent ranks of Sergeant Major and Sergeant Major of the Marine Corps) in the U.S. Marine Corps. Master Gunnery Sergeants are staff non-commissioned officers (SNCOs), and are assigned a pay grade of E-9.
Master Gunnery Sergeants are sometimes referred to by the nickname "Master Gunns" or "Master Gunny." These nicknames are unacceptable in formal or ceremonial situations, and, at the rank holder's discretion, may also be unacceptable for use by lower-ranking Marines.
Establishment of the rank in its current form and paygrade occurred during sweeping reorganization of ranks and paygrades in 1958 and 1959. The rank was included, along with the rank of Master Sergeant, in a new program for the paygrades of E-8 and E-9 which allowed senior SNCO billets to be filled by occupational specialists. This move was designed to officially acknowledge the ever-increasing complexity of modern warfare, while still maintaining the First Sergeant and Sergeant Major programs, with their historic command prestige. During and prior to World War II, this was reversed; the Sergeant Major was an administrative position whilst the Master Gunnery Sergeant was part of the S-3 section and enforced discipline.
In their annual performance evaluations, called "fitness reports," eligible Gunnery Sergeants indicate whether they wish to be considered for promotion to Master Sergeant or First Sergeant, and thus whether they enter the promotional track for Master Gunnery Sergeant or Sergeant Major. Once promoted, the promotional track is usually permanent; with lateral movement between the two programs very uncommon.
One of the major differences between the two E-9 ranks is that Master Gunnery Sergeants retain their Military Occupational Specialty (MOS), while Sergeants Major are given a new MOS to reflect their general command focus. This reinforces the Master Gunnery Sergeant's role as a provider of technical military leadership.