Hieromartyr Irenaeus of Sirmium

Hieromartyr Irenaeus, bishop of Sirmium, served in the city of Sirmium (present-day Sremska Mitrovica, Serbia) among the Danube Slavic population in the late 3rd–early 4th century.

During the persecution of Christians under Emperor Diocletian, he was arrested, tortured, and pressured to sacrifice to the pagan gods, but firmly confessed his faith in Christ before the governor Probus. He was condemned to death by the sword, and his body was cast into a river — sources vary between a tributary of the Sava and the Sava itself.

His martyr acts survive in both Latin and Greek recensions, attesting to early and widespread veneration.

His feast is commemorated on March 26/April 8.

NOTE: explicitly distinguished from St. Irenaeus of Lyon (2nd c., the famous anti-Gnostic theologian, author of "Against Heresies," also titled "hieromartyr" in Orthodox liturgical tradition, but known primarily as a Church Father rather than through a developed martyrdom account).