Master gunnery sergeant (MGySgt) is the 9th and highest enlisted grade in the United States Marine Corps.

[1] As E-9s, they tend to serve for about 15 to 30 years, and advise commanders on subjects relating to the enlisted.

The master gunnery sergeant insignia consists of a exploding bomb centered vertically between three chevrons and four rockers.

Master gunnery sergeants (MGySgts) with an infantry Military Occupational Specialty (MOS) serve in the billet of operations chief, as the senior staff non-commissioned officer in the operations section of an infantry battalion, or higher level (e.g., MEU, infantry regiment, MEB, Marine division, or MEF) headquarters.

This reinforces the master gunnery sergeant's role as a provider of military leadership, technical acumen, and mastery of their MOS.