Saints Nazarius and Celsus were two martyrs of whom nothing is known except the discovery of their bodies by Saint Ambrose.
According to Paulinus the Deacon's Vita Ambrosii, Ambrose, at some time within the last three years of his life, after the death of the Emperor Theodosius, discovered in a garden outside the walls of Milan the body of Saint Nazarius, with severed head. Nazarius's blood was reportedly still liquid and red when his body was exhumed by Ambrose. Ambrose had it carried to the Basilica of the Apostles. In the same garden Ambrose likewise discovered the body of Saint Celsus, which he had transported to the same place. The Catholic Encyclopedia states: "Obviously a tradition regarding these martyrs was extant in the Christian community of Milan which led to the finding of the two bodies."