Dictionary of National Biography, 1885-1900/O'Brien, Murtough
O'BRIEN, MURTOUGH (d. 1119), king of Munster, called in Irish Muircheartach mór Ua Briain, was son of Turlough O'Brien [q. v.], king of Munster. He first appears in the chronicles as righdhamhna Mumhan, royal heir of Munster, in 1075, when he fought a battle at Ardmonann, near Ardee, co. Louth, with the Oirghialla, the people of that region, and was defeated with much slaughter, reaching home without any spoil. In 1084 O'Rourke and other Connaughtmen invaded Leinster, and were met by forces from Leinster, Ossory, and Munster, under Murtough, at Monecronock, co. Kildare, on 29 Oct., and, after severe fighting, were defeated. In 1087 he defeated the Leinstermen near Howth, co. Dublin, but in the following year he was himself defeated, in his own country, by Roderic O'Connor, and soon after Limerick was burnt. He sailed up the Shannon in the spring, and ravaged the shores of Lough Ree, but was defeated near Athlone on his way home. He invaded Meath in 1090, and fought its king, at Moylena, King's County, with ill success, but was able later in the year to make a foray to Athboy, co. Meath. He plundered Clonmacnoise and attacked Connaught in 1092, and made another expedition into Connaught in 1093, and another, with no success, in 1094. In the same year he made two expeditions into Meath. His father having died in 1086, he was now king of Munster, and in 1096 rebuilt Ceanncoradh, the royal residence of the chief of the Dal Cais. In 1097—long known as ‘bliadhain na ccnó bfionn’ (year of the fine nuts), from the abundance of the hazel nuts—he made a warlike expedition to Louth, but the archbishop of Armagh interposed and made peace. In 1098 he made a second unsuccessful northern march, and also ravaged Magh Dairbhre in Meath. He attempted the invasion of Ulster by way of Assaroe, co. Donegal, in 1100, but failed. At the same time he tried to persuade the Danes to attack Derry from the sea. In 1101, however, he crossed the Erne at Assaroe, and, marching rapidly north, captured Ailech, the residence of the northern kings. He ruined it in revenge for the sack of Ceanncoradh by Domhnall O'Lochlainn [q. v.], king of Ailech, and ordered, says an old verse, each soldier to carry off a stone from it. Many of the stones of Ailech are heavy, and even before the late restoration a great many, in spite of the king's order, remained in their places. He then crossed the Ban at Camus Macosquin, took hostages of Ulidia, or Lesser Ulster, and completed the circuit of Ireland in six weeks, returning from the north by the famous ancient road called Slighe Midhluachra, which led from Ulster to Tara. This expedition was long known as ‘an slóighedh timchill’ (the circuitous hosting). He granted the Rock of Cashel and the town round it, which up to this time had been the royal residence of the kings of Munster, to the church in the same year. The ancient stone-roofed cathedral, which now stands on the rock, was built rather less than forty years after this event. He plundered Magh Murtheimhne, co. Louth, in 1104, Meath in 1105, Breifne in 1109, and Clonmacnoise for the second time in 1111. In 1113 he fought for Donnchadh, king of Ulidia, against the Cinel Eoghain, Cinel Conaill, and the Oirghialla, but was defeated. He fell ill in 1114, became greatly emaciated, and seemed so devoid of strength that Dermot O'Brien assumed the kingship of Munster; but in 1115 Murtogh took him prisoner and made an expedition into Leinster. He died, probably of pulmonary consumption, which began in 1114, on 10 March 1119, and was buried in the church of Killaloe.
His wife's name was Dubhchobhlaigh, and she died in 1086.
[Annala Rioghachta Eireann, ed. O'Donovan, vol. ii.; Annals of Ulster (Rolls Ser.), ed. MacCarthy, vol. ii.; Colgan's Acta Sanctorum Hiberniæ, Louvain, 1645; Ordnance Survey of the County of Londonderry, Dublin, 1837.]