Derry (DERIA), Diocese of (DERRIENSIS), includes nearly all the County Derry, part of Donegal, and a large portion of Tyrone, Ireland; it is a suffragan of Armagh. The diocese owes its origin to the monastic establishment founded there by St. Columba between 546 and 562. But there does not seem to have been a bishop resident at Derry before Gervase O’Cervallen (c. 1230).
The entry in the “Annals” by which O’Brolchain is represented as Bishop of Derry is due to a mistranslation. He was merely the superior of the Columban monastic houses, and was accorded the honor of a seat in the assembly of the bishops. The present Diocese of Derry was formed by a union of the old Sees of Pathlure and Ardstraw founded by St. Eugene, at what time cannot be accurately determined, and it was fully defined about the middle of the thirteenth century. The ancient monastery of Derry was one of the most important in Ireland, and eventually the chief house of the Columban monks. Gilla Mac-Leag (Gelasius) who succeeded St. Malachy as Archbishop of Armagh (1136) had been abbot of the monastery.
After the formation of the diocese in the thirteenth century the succession of bishops was uninterrupted till the Reformation period. Redmond O’Gallagher, appointed bishop in 1569, was one of the leading ecclesiastics in the province of Armagh at that period. He was appointed Administrator of Armagh during the absence of the primate in 1575, and according to a State paper (1592) he seems to have been the most active upholder of the Catholic Church in Ulster. He was killed by a body of soldiers in 1601. From 1601 till 1683 the Diocese of Derry was administered by vicars. From the appointment of Bernard O’Cahan in 1683, the line of bishops in Derry has been continued with-out interruption.
The population of Derry according to the census of 1901 was 222,505, 127,387 of whom were Catholics. It is divided into thirty-nine parishes, two of these being mensal parishes; the remainder are held by parish priests. The number of priests in the diocese is about 108. There is no chapter (1908), nor is there any house of the regular clergy in the diocese. The seat of the bishop is in the city of Derry where are also situated the new cathedral and St. Columb’s College which serves at the same time the purpose of a seminary and a general intermediate school, and is one of the most successful educational establishments in Ireland. There is also a flourishing intermediate school at Omagh conducted by the Irish Christian Brothers.
The Sisters of Mercy have convents in Derry, Moville, Strabane, and Carndonagh; the Loretto Community have a house at Omagh, while the Sisters of Nazareth conduct a home for the aged of both sexes and one for children in Derry. The primary schools are conducted according to the rules of the Board of National Education, while the Model Schools in Derry have been completely boycotted by the Catholic population.