Musashi Miyamoto is a Saber-class Servant able to be summoned by Ritsuka Fujimaru in the Grand Orders of Fate/Grand Order.
A swordsman from the early Edo period, Musashi was renowned as the strongest swordsman in the history of Japan. He founded the Niten Ichi-ryuu school of swordsmanship; a martial art that involved the dual-wielding of a katana and wakizashi. However her circumstances are somehow different from the Musashi that left his name in history.
(Source: TYPE-MOON Wiki)