Connor O'Brien, 3rd Earl of Thomond

Connor O'Brien, 3rd Earl of Thomond (1534?–1581), called Groibleach (or Long-nailed), grandson of Conor O'Brien (d. 1539); succeeded to the earldom, 1553; his right to the lordship of Thomond was disputed by his uncle, Donnell; confirmed in his possessions by Thomas Radclyffe, 3rd Earl of Sussex in 1558, who proclaimed his uncles traitors, though peace was not established until 1565. He intrigued with Fitzgerald in 1569, and fled to France; returned to Ireland and received pardon, 1571, with the restoration of his lands, 1573.

O'Brien, was, called Groibleach, or the "long-nailed", was the eldest son of Donough O'Brien, 2nd Earl of Thomond, and Helen Butler, youngest daughter of Piers Butler, 8th Earl of Ormond. He succeeded to the earldom on the death of his father in April 1553. His right was challenged by his uncle Donnell, who was formally inaugurated O'Brien and chief of the Dal Cais. Obliged to surrender Clonroad, the usual residence of the O'Briens, Conor retired to the castle of Doonmulvihill, on the borders of Galway, where he was besieged by Donnell, but relieved by his kinsman Thomas Butler, 10th Earl of Ormond.

Subsequently Donnell petitioned for official recognition as chief of Thomond, and St. Leger, though unable to grant his request, promised to write to Queen Mary in his favour. Matters continued in this uncertain state till the summer of 1558, when the Earl of Sussex, having marched to Limerick with a large army, caused Donnell and Teige and Donough, sons of Murrough, 1st Earl of Thomond, to be proclaimed traitors, and Conor to be reinstated in his possessions. Donnell took refuge with Maguire in Fermanagh, and Teige and Donough found a powerful protector in Gerald FitzGerald, 15th Earl of Desmond.

Peace prevailed for a brief season, and Conor won Sussex's approbation for his good execution of justice. But in 1559 Teige and Donough returned to Inchiquin, and not merely defied Conor's efforts to oust them, but, with the assistance of the Earl of Desmond, actually inflicted a sharp defeat on him and his ally, the Earl of Clanricarde, at the Battle of Spancel Hill. Teige was shortly afterwards arrested by Lord-justice William FitzWilliam, and confined in Dublin Castle ; but early in 1562 he managed to escape, and, being joined by Donnell, they opposed a formidable army to the Earl of Thomond. With the help of some ordnance lent him by Sussex, Thomond succeeded in wresting Ballyally and Ballycarhy from them; and eventually, in April 1565, after reducing the country to a wilderness, Donnell consented to surrender his claim to the lordship of Thomond on condition of receiving Corcomroe. War broke out again in the following year ; but the resources of the combatants were exhausted,and Sidney, when he visited Limerick in April 1567, described it as utterly impoverished owing to the Earl of Thomond's "insufficiency to govern".

The suspicion with which he was regarded made him discontented, and on 8 July 1569 he entered into league with the "arch-rebel" James Fitzmaurice Fitzgerald (d. 1579). In February 1570 he attacked the President of Connaught, Sir Edward Fitton, at Ennis, and compelled him to seek refuge in Galway. A strong force under the Earl of Ormond was immediately despatched against him, and a few weeks later he submitted unconditionally. But being "seized with sorrow and regret for having surrendered his towns and prisoners", and determined never to "submit himself to the law, or to the mercy of the council of Ireland", he fled in the beginning of June to France.

There he introduced himself on 18 July to Sir Henry Norris, 1st Baron Norreys, the English ambassador, and, after protesting his loyalty, begged him to intercede with the Queen Elizabeth for his pardon. Norris, who thought him a "barbarous man", wanting "neither vainglory or deceitfulness, and yet in his talk very simple", soon became aware that he was intriguing with the French court, and urged Elizabeth to coax him home at any price. Elizabeth, though she spoke of him as a "person of small value" and declined to pardon him beforehand, was sufficiently alive to his power to do mischief, and promised if he returned to give his grievances a favourable hearing. But Thomond showed no disposition to leave Paris, and Norris was forced to lend him a hundred crowns and make endless promises before he would consent to take his departure.

He returned to Ireland in December, and, having made public confession of his treason to Sir Henry Sidney, he was pardoned. Subsequently, in April 1571, he made surrender of all his lands to the queen. He obtained permission to go to England to solicit their restoration, but, owing to the rebellion of the Earl of Clanricarde's sons, his presence was required in Ireland. He won the approval of the lord-deputy and council, and warrant was apparently given in June 1573 for the restoration of his lands. In December 1575 he went to Cork to show his respect to the lord-deputy, Sir Henry Sidney, whom he attended to Limerick and Galway, whither the principal men of Thomond repaired to him. "And finding that the mutuall Hurtes and Revenges donne betwixt the Earle and Teige MacMurrough Avas one great Cawse of the Ruyne of the Country", Sidney "bounde theim by Bondes, in great sommes", to surrender their lands, and to submit to the appointment of Donnell, created Sir Donnell O'Brien, as sheriff of the newly constituted county of Clare. This arrangement, though acquiesced in, was naturally displeasing to Thomond, and he was reputed to have said that he repented ever "condescending to the queen's mercy".

The arrangement did not put an end to the disputes between him and Teige, and in 1577 Sir William Drury was compelled to place the county under martial government. Thomond thereupon repaired to England, and on 7 October warrant was issued for a new patent containing the full effect of his former patent, with remainder to his son Donough, baron of Ibrickan. He returned to Ireland about Christmas; but before his arrival, according to the "Four Masters", "the marshal had imposed a severe burden on his people, so that they were obliged to become tributary to the sovereign, and pay a sum of ten pounds for every barony, and this was the first tribute ever paid by the Dal Cais." Thomond, however, seems to have lived on good terms with the new president of Connaught, Sir Nicholas Malby. He died, apparently, in January 1581, and was succeeded by his eldest son, Donough, baron of Ibrickan and 4th earl of Thomond.

Conor O'Brien first married Slaney O'Brien and they had a son, Donough, who died in 1635. He then married Ellen, daughter of Donald MacCormac MacCarthy Mor and widow of James FitzGerald, 14th Earl of Desmond; she died in 1560, and was buried in Muckross Abbey. He then married Una, daughter of Turlough Mac-i-Brien-Ara, with whom he had two sons: Teige (restorer of Dromore Castle, near Ruan), and Daniel, created 1st Viscount Clare and three daughters. Honora, first wife of Thomas Fitzmaurice, 18th Lord Kerry; Margaret, second wife of James Butler, 2nd Lord Dunboyne; and Mary, wife of Turlough Roe MacMahon of Corcovaskin.