Diarmait ua Tigernáin

Diarmait ua Tigernáin (Diarmaid, Dermot) was abbot and bishop of Armagh and reposed around 852. He is venerated as a saint in the Western Church, under the name Saint Dermot; his day is 24 April.

In the medieval Irish church the abbot of Armagh also served as bishop. In 834 Diarmait was named bishop to succeed Eógan Mainistrech mac Ainbthig. In 835 he was driven from his see by the usurper Foraunan. He claimed his rights, however, and in 836 collected his cess in Connacht, bringing with him the Bachal Isu (the reputed staff of Jesus), the Book of Armagh and Saint Patrick's Bell, the first two being important symbols of the authority of the bishop of Armagh. With the support of Fedelmid mac Crimthainn he was installed at Armagh in 839, though the see continued to be contested. During his bishopric the Scandinavians under Turgesius seized Armagh in 841 and leveled the churches. By 848 he was in sole control. In 851 he attended the meeting at which Máel Sechnaill mac Máele Ruanaid was acknowledged as High King by the men of Ulster. The Annals of Ulster describe him as one of "the wisest of the doctors of Europe".