Lough Key
Title
Lough Key
Also Known As
Holy Trinity Island, Insula Sanctissimae Trinitatis de Loch Qyu, Lacus viri dicti Ké, Loch Cé, Loghkee, Louchque, Lougkca
Dates
Founded 1215; dissolved 1608
Dedication
Holy Trinity
Affiliation
Medieval Diocese
Circary
History
Monastic communities existed on Trinity Island in Lough Key from the early Middle Ages, but the Premonstratensian community was founded in 1215 as a priory by Clarus Mag Máilin, archdeacon of Elphin, on land given by Cathal, king of East Bréifne. Some Cistercian monks from Boyle Abbey joined the community in the 1220s. From ca. 1235, Lough Key was elevated to the rank of an abbey.
The famous Annals of Loch Cé were written at the community. The abbey survived the initial Dissolution, but was suppressed by James I in 1608.
The site was excavated in the 1990s.
The famous Annals of Loch Cé were written at the community. The abbey survived the initial Dissolution, but was suppressed by James I in 1608.
The site was excavated in the 1990s.
Heads of Community
Abbots
Matthew I, ?-1235
Gilla Ísu mac in Liathána Ó Conchobair (Gelasius O'Connor), 1260-1285
Edruth McCraith, ?-1291
Cathal Ó Conchobair (Carolus O'Connor), 1310-1343
Matthew II, bef. 1381
Macharias, 1381-?
Matthew III, ?-1397
Cornelius Mac Buassaid, 1397-?
Congall, ?-1421
Thady McDiarmada, 1421-1428, 1444
Rory I O'Carraid, 1428-1442
Mauritius McDonnchayd, 1442-1444
Magnus McDonnchada, 1444-1504
Rory II McDermot, 1548-1568
Bernardus O'Beirne, 1660-1668
Matthew I, ?-1235
Gilla Ísu mac in Liathána Ó Conchobair (Gelasius O'Connor), 1260-1285
Edruth McCraith, ?-1291
Cathal Ó Conchobair (Carolus O'Connor), 1310-1343
Matthew II, bef. 1381
Macharias, 1381-?
Matthew III, ?-1397
Cornelius Mac Buassaid, 1397-?
Congall, ?-1421
Thady McDiarmada, 1421-1428, 1444
Rory I O'Carraid, 1428-1442
Mauritius McDonnchayd, 1442-1444
Magnus McDonnchada, 1444-1504
Rory II McDermot, 1548-1568
Bernardus O'Beirne, 1660-1668
Status
Priory, then abbey
Archival Sources
Dublin, National Library of Ireland
Ms. G. 213
MS 22,139/10/2
Dublin, Trinity College Dublin
MS 1293 (Annals of Loch Cé)
Ms. G. 213
MS 22,139/10/2
Dublin, Trinity College Dublin
MS 1293 (Annals of Loch Cé)
Reference
Bibliography
Clyne, Miriam. “1991:112 - Holy Trinity Abbey, Trinity Island, Roscommon.” Excavations.ie, 1991. https://excavations.ie/report/1991/Roscommon/0001171/.
———. “Archaeological Excavations at Holy Trinity Abbey Lough Key, Co. Roscommon.” Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature 105, no. 2 (January 2005): 23–98. http://www.jstor.org/stable/25506230.
———. “The Rental of Holy Trinity Abbey, Lough Cé.” In Medieval Lough Cé: History, Archaeology and Landscape, edited by Thomas Finan, 67–96. Dublin: Four Courts Press, 2010.
Healy, John. “The Annals of Lough Key.” The Irish Monthly 6 (1878): 273–83. https://www.jstor.org/stable/20502186.
Hennessy, W.M. The Annals of Loch Cé : A Chronicle of Irish Affairs from A.D. 1014 to A.D. 1590. London, 1871. https://archive.org/details/annalsoflochcc01hennuoft.
O’Dwyer, B.W. “The Annals of Connacht and Loch Cé and the Monasteries of Boyle and Holy Trinity.” Proceedings of the Royal Irish Academy: Archaeology, Culture, History, Literature 72 (1972): 83–101. https://www.jstor.org/stable/25506262.
O’Flanders, A. “The Annals of Lough Key (Loch Cé).” Analecta Praemonstratensia 6 (1930): 410–14.
Image Credit
R. Armstrong, "The Shrine of the Holy Trinity in the ruins of Trinity Abbey" (19th century). National Library of Ireland.
Files
Collection
Citation
“Lough Key,” A Premonstratensian Atlas, accessed October 16, 2026, https://yvonneseale.org/atlas/items/show/33.
Geolocation
Item Relations
| Item: Lough Oughter | DependentOn | This Item |
| Item: Athmoy | DependentOn | This Item |