The Jedi Battlemaster, or simply Battlemaster, was the title for the premier lightsaber instructor of the Jedi Order or its enclaves. The Battlemaster oversaw all lightsaber instruction and was responsible for electing new instructors.
During the Old Republic Era, there was more than one single Jedi Battlemaster. Yavin, Hoth, Ilum, Tatooine, Quesh, and Alderaan each had a Jedi Battlemaster guarding and instructing the front lines. It was understood that in this era, the title of Battlemaster was given to Jedi who had gone above and beyond in combat during the conflict.
With the upcoming threat of the Eternal Empire, the majority of Jedi Battlemasters were killed or went into hiding.