Master Chief

Master chief was a military rank most commonly used in navies and militias.

Republic/Imperial Military
Master chief was introduced among certain crew officers in the Republic Judicial Forces and later carried over to the Republic Navy during the Clone Wars. Some Republic mercenaries and penal troopers were also granted the rank of master chief. The rank remained actively used within the early Imperial Navy though was later renamed "Chief Petty Officer".

Rebel Alliance
In the Rebel Navy, the rank master chief was often given to the leaders of starfighter squadrons as well as the captains of Rebel privateer ships.

Mandalorians
The master chief title (Kalyr'alor in the Mandalorian language) was also used by some local militia commanders throughout the Mandalore sector, both on the ground and in space.