| Jurisdiction: | Diocese |
| Ardagh and Clonmacnoise | |
| Latin: | Dioecesis Ardachadensis et Cluanensis |
| Local: | Deoise Ardach agus Chluain Mhic Nóis |
| Country: | Ireland |
| Metropolitan: | Archdiocese of Armagh |
| Territory: | Most of counties Longford and Leitrim and parts of counties Cavan, Offaly, Roscommon, Sligo and Westmeath |
| Province: | Province of Armagh |
| Area Sqmi: | 940 |
| Population: | 89,100 |
| Population As Of: | 2015 |
| Catholics: | 76,626 |
| Catholics Percent: | 86 |
| Denomination: | Roman Catholic |
| Rite: | Roman Rite |
| Established: | 1756 |
| Cathedral: | St. Mel's Cathedral, Longford |
| Patron: | St Mel |
| Bishop: | Paul Connell, Bishop of Ardagh and Clonmacnoise |
| Bishop Title: | Bishop |
| Metro Archbishop: | Eamon Martin |
| Vicar General: | Monsignor Patrick Early |
| Emeritus Bishops: | Colm O'Reilly |
| Map: | Roman Catholic Diocese of Ardagh map.png |
| Website: | ardaghdiocese.org |
The Diocese of Ardagh and Clonmacnoise (Latin: Dioecesis Ardachadensis et Cluanensis; Irish: Deoise Ardach agus Chluain Mhic Nóis) is a Latin Church diocese of the Catholic Church in Ireland.
The diocese is entirely within the Republic of Ireland and contains most of counties Longford and Leitrim, with parts of counties Cavan, Offaly, Roscommon, Sligo and Westmeath. The main towns in the diocese are Athlone, Ballymahon, Carrick-on-Shannon, Edgeworthstown, Granard and Longford.
The union of the sees of Ardagh and Clonmacnoise, which had been proposed in 1709, was carried into effect following the death of Stephen MacEgan, Bishop of Meath on 30 May 1756, who had been administering the see of Clonmacnoise.[1] [2] Augustine Cheevers, Bishop of Ardagh, was translated to the see of Meath on 7 August 1756, and Anthony Blake was appointed as the first bishop of united see of Ardagh and Clonmacnoise on 11 August 1756.[1] [2]
On Christmas Day 2009, St Mel's cathedral in Longford was destroyed by fire. Bishop O'Reilly said that the building is "just a shell" and "burned out from end to end". The bishop said construction on the cathedral began in 1840 and he described it as a flagship Cathedrals of the midlands. After a long investigation the cause of the fire was traced back to a brick lined chimney at the rear of the cathedral. St Mel's was restored, reopening in 2014.
See main article: Bishop of Ardagh and Clonmacnoise. On 5 April 2023, Paul Connell was appointed the Bishop of Ardagh and Clonmacnoise by Pope Francis.
The following are the current parishes in the diocese (official names in italics where they differ from the currently-used names)