Leontius of Caesarea was a 4th-century bishop of Caesarea Mazaca, located in Cappadocia. He is recognized as a saint within the Catholic and Orthodox traditions. A significant figure in early Christian history, he participated in the First Council of Nicaea in 325. He is notably remembered for his lifelong connection to Gregory the Illuminator, whom he had known since childhood, and for later consecrating Gregory as the patriarch of the Armenians.