Kiritsugu Emiya (衛宮 切嗣, Emiya Kiritsugu?) is the Master of Saber in the Fourth Holy Grail War of Fate/Zero. He is the husband of Irisviel von Einzbern, the father of Illyasviel von Einzbern, and the adoptive father of Shirou Emiya. He is the main protagonist of Fate/Zero and has a minor role in Fate/stay night. He was a freelancer and notoriously known as the Magus Killer (魔術師殺し, Majutsushi-goroshi?).

Kiritsugu is a brooding and conflicted person. In his youth, he wished to become a Hero of Justice and protect the weak. He is often haunted by Shirley's question about what he wants to become, and how she believed he alone had the power to change the world. His hesitation to kill his first love when she became a Dead Apostle resulted in the death of everyone on the Island. Kiritsugu, realizing that his father was the cause of this and he would continue his Dead Apostle experiment, hardened his resolve and killed his father to prevent more deaths. Kiritsugu then resolved to make meaning and worth from the murder of his father. Only by hunting and assassinating all heretic magi like his father could he truly prevent such tragedies from occurring again. He lost all traces of youthful innocence after having spent his life going through countless battles while trying to obtain a utopia that could never be fulfilled, which caused him to become incredibly self-loathing. After learning of the Grail, he sought to use it to create the utopia from his dream. He feels no emotion from personal victories over his targets, seeing them as nothing more than successful taunts with calculated resolutions.