The area was the site of the battle of Fidhnacha in 1094. Fenagh Abbey is one of the oldest monastic sites in Ireland, believed to date back to the earliest period of Celtic monasticism. The founder was St. Caillín, thought to have arrived in Fenagh from Dunmore in County Galway in the 5th century. The Abbey had a monastic school, and was "''celebrated for its divinity school, which was resorted to by students from every part of Europe". Magnus, son of Muirchertach Muimnech, wrote in 1244:
Fedlimid mac Cathail Chrobdeirg made an immense hosting eastwards into Brefne against O Raigillig, to avenge his fosterson and kinsman, Tadc O Conchobair. They encamped for a night at Fenagh. At that time there was no roof on the church of Fenagh, and the coarb was away that night. And as he was not present, the common soldiers of the host burned the huts and tents which were inside the church, without permission of their leaders, and the coarb's foster-child, God's gift, was suffocated. Now learned men relate that the coarb received this foster-child by finding him on a large stone which stood in that place, and never knew of his having either mother or father; and the coarb loved him and gave him, as it is said, milk from his own breasts. Next day he came to them in anger and indignation at the death of the boy, requiring O Conchobair to pay the blood-fine for his foster-child, and O Conchobair said he could choose what fine he pleased. 'I choose' said he 'the best man among you, as compensation for the child of God whom you have burnt.' 'That' said O Conchobair 'is Magnus, the son of Muirchertach Muimnech.' 'Nay, not so,’ said Magnus 'but he who is leader of the host.' 'I will not go from you so' said the coarb 'until I get the fine for my foster-child.' After this the host departed from that place, and the coarb followed them to Ath na Cuirre on the Yellow River, which was flowing over its banks, so that they could not cross it till they broke up the spital-house of John the Baptist, which stood beside the ford, and used its materials to bridge the river for the host to pass across. Magnus son of Muirchertach Muimnech and Conchobar son of Cormac Mac Diarmata went into the house, and Magnus spoke to a man who was above him, at work on the house-breaking; 'That' said he, pointing upwards with the chape of his sword, 'is the nail which keeps the house from falling.' As he spoke, a rafter fell on his head and smashed it to pieces on the spot. He was buried outside the doorway of the church of Fenagh, and thrice the capacity of the Bell of the Kings of silver and thirty horses were given as an offering with him. Thus, then, did the coarb of St. Caillin at last recover compensation for his fosterling of God from them. A beautiful monument of carved stone with an excellently wrought stone cross was afterwards made over him, but after a while the Ui Ruairc in their enmity demolished it.
At Fenagh, two church ruins stand on the site of an earlier monastery founded by St. Caillin in the 6th century. The main ruins of the Gothic church have an east window of unusual design and a relief-carved 17th-century penal cross. A number of standing stones in the vicinity represent the petrified bodies of druids who tried to expel St. Caillin from Fenagh. There are a number of other prehistoric remains located in or near the village. A portal tomb at the north of the village is said to be the burial place of King Conall Gulban. 19 Gaelic kings are said to be buried in the graveyard. There was also a divinity school at Fenagh. It is believed that community life continued until 1652, when Cromwellian soldiers sacked it. It was damaged by cannon fire during the Williamite wars in 1690, and the last service was said in 1729. The site is on the northern shore of Fenagh Lough.
The Book of Fenagh was completed at the monastery in 1516, and a copy is now kept at the Royal Irish Academy. It was written in Irish, and contains verse and prose of the "life" of St Caillin of Fenagh transcribed and translated from the, now lost, Old Book of St. Caillin. The original Old Book of St. Caillin apparently "only contained prose" but the Book of Fenagh / Leabar Chaillín / Leabar Fidhnacha of 1516, contained both prose and verse. Some poems relevant to the politics of 11th-13th-century Tyrconnell, are thought to date from an earlier period than the rest of the manuscript. The Book of Fenagh, in Irish and English, is available to read for free.
Notable residents
John McGahern, writer who lived, wrote and farmed in Fenagh for the last 30 years of his life. Much of his inspiration for Amongst Women, That they May Face the Rising Sun and Memoir comes from the area.
