He was a bishop in the city of Tagrit in Mesopotamia. Emperor Theodosius the Great sent him to the Persian emperor Izdegerd in 380. Because of his virtues, he gained great respect among the Persians, especially when he healed the insane daughter of the emperor. Then he asked him for, and received, the relics of 400 holy martyrs who suffered for Christ in Persia during the time of Emperor Sapor, in the 4th century, and later. He transferred these relics to the Christian empire and founded a new city in their memory – Martyropol. Saint Marut described many of the sufferings of the Persian martyrs, the Martyrology. He himself witnessed some of the sufferings he described. He gave up his soul to the Lord in the year 422, on the day when the city of Martyropol, which he founded, was consecrated.

The twelve holy martyrs: Pamphilus, Valens, Paul, Porphyry and others. The holy venerable martyr Romanus.