Muramasa may refer to:
Sengo Muramasa was a Japanese swordsmith of the Muromachi Period famous for his extremely sharp blades, but was said to be insane. His works are identified by the unusual but skilled properties of having symmetrically matching temper lines on both sides of the blade, fish belly styled tangs, and clean cut boundaries of temper lines, showing the focus of practicality than a balance. The blades forged by him were involved in numerous famous yet unfortunate accidents in the early years of the Tokugawa Shogunate run Edo Period that led to the legends of his swords being evil and bloodthirsty to the point that once drawn, could not be returned to their scabbards without having first drawn blood, even if it required the wielder to commit suicide, and led to his swords being banned. He is famously compared to Masamune in Japanese legend as blacksmiths representative of their times; Masamune of the golden age of katana in the prosperous times of Kamakura, with Muramasa of the turbulent and violent warring age of the Sengoku.