The diocese of Ardagh and Clonmacnois is spread over parts of seven counties in the centre of Ireland. It includes almost all of Longford, half of Leitrim and parts of Westmeath, Offaly, Cavan, Roscommon and Sligo. It covers an area of 2,437 sq. km. At the end of 1996, the population was 70,748, of which 69,612 were Catholic. It has 64 priests at present, and a total of 41 parishes.
The Diocese of Ardagh, as distinct from that of Clonmacnois, with which it is now united, takes its name from the village of Ardagh, now a picturesque village in County Longford. We know that St. Patrick came to Ardagh and founded a Church there from two of our earliest sources of information about his life, the Memoir of Tirechan in the Book of Armagh and the Tripartite Life. The Diocese of Ardagh has as its Patron and first Bishop one of St. Patrick’s immediate entourage, his friend, and, according to some, his nephew, St. Mel. Thus the history of Ardagh goes back to the dawn of Christianity in Ireland.
The most celebrated monastery for many centuries in the Ardagh part of our Diocese was that of Inis Clothrann in Lough Ree. The Island is supposed to have got its name from Clothra, sister of Maedhbh, the famous Queen of Connaught. Sometimes the island is referred to as Inis Dhiarmada, from the saint who founded the monastery. Diarmuid is said to have been friend and spiritual director to St. Ciaran of Clonmacnois.
Ardagh was erected as a Diocese by the Synod of Kells (1152) and was made a suffragan of Armagh. In the thirteenth century a dispute arose as to whether it was subject to Tuam or Armagh. Gregory IX ordered an investigation in 1235 and it was resolved in favour of Armagh.
Of the fifty-nine listed Bishops of Ardagh two were Franciscans, two Augustinians, one a Cistercian and one a Vincentian. For long periods in the seventeenth century and early eighteenth century the Diocese was ruled by Vicars Apostolic. The Diocese featured in the ministry of St. Oliver Plunkett whose relative, Dr. Patrick Plunkett, a Cistercian, was Bishop of the Diocese from 1647 to 1669. Evidence of the involvement of St. Oliver is to be seen in the register of priests from 1704. Several of these were ordained by him.
The episcopate of Dr. Cheevers (1751-56) was marked by the joining of Clonmacnois to Ardagh. It appears that Bishop Cheevers was administering the Diocese of Clonmancois on behalf of the Bishop of Meath to which Clonmacnois had been attached when he became Bishop. He applied to the Holy See to have Clonmacnois united to Ardagh, saying the poverty of the Diocese of Ardagh was such that he needed additional territory. When he was translated to Meath in 1756 he sought to have this request reversed but by then the Holy See had acceded to his earlier request and refused to change its mind.