Dictionary of National Biography, 1885-1900/O'Brien, Conchobhar
O'BRIEN, CONCHOBAR (d. 1267), king of Thomond, called ‘na siudaine,’ from the name of the wood near Belaclugga, co. Clare, where he was slain (Magrath, Caithreim), was son of Donogh Cairbrech O'Brien [q. v.], and succeeded his father in 1242. In 1257 he had some successes against the English, and in 1258 sent his son Tadhg to Caoluisce on Lough Erne to treat with Brian O'Neill. In the ‘Annals of Clonmacnoise’ and in the ‘Annals of Ulster’ it is stated that the result was that it was agreed that Brian O'Neill should be king of Ireland, and that the O'Briens, O'Connors, and O'Kellys gave him hostages. In the ‘Caithreim Thoirdhealbhaigh,’ however, a better account is given of this meeting, and the date is fixed six years earlier. Tadhg O'Brien, says the author of the ‘Caithreim,’ sent a hundred horses to O'Neill as a present and sign of his father Conchobhar's supremacy. O'Neill sent them back, with two hundred others, with grand trappings, in token of his own supremacy, and so the meeting broke up. After the death of his son Tadhg in 1248 O'Brien seldom appeared in public, and attended no feasts. His subjects refused to pay his royal rents and dues. He then made a muster of Clancullen under Sioda MacNeill MacConmara, and of Cinel Domhnaill under Aneslis O'Grady, and they, with his son Brian Ruadh, marched into the cantred of O'Blood and carried off captives and spoil from Birr, King's County, to Knockany, co. Limerick, and from the Eoghanacht of Cashel, co. Tipperary, to Killaloe, co. Clare. These they brought to Conchobhar at Clonroad, where he had made a permanent camp with earthworks. Conchobhar himself, with the O'Deas and O'Cuinns, under Donnchadh O'Dea, and O'Haichir with his force, marched to O'Lochlainn's country, co. Clare. Conchobhar Carrach O'Lochlainn met this army at Belaclugga, and defeated and slew Conchobhar O'Brien. This was in 1267. He was buried in the monastery of East Burren, now the abbey of Corcomroe (O'Grady's translation of Caithreim). His tomb and full-length effigy wearing a crown are still to be seen in the abbey. O'Brien married Mór, daughter of MacConmara, and had three sons: Tadhg, who died in 1248; Brian Ruadh [q. v.], king of Thomond; and Seoinin. His son Seoinin and his daughter, who was married to Ruaidhri O'Grady, were killed by Murtough O'Brien; but Murtough was soon after killed, and Brian Ruadh became lord of Thomond and chief of the Dal Cais.
[Annala Rioghachta Eireann, ed. O'Donovan, vol. iii.; Annals of Ulster, ed. MacCarthy (Rolls Ser.); Annals of Loch Cé, ed. Hennessy; manuscript text of Caithreim Thoirdhealbhaigh, with translation and notes, and extract from Historical Book of the O'Mulconry's MS. kept to 1608, kindly lent by S. H. O'Grady, esq.]