Barnabas O'Brien, 6th Earl of Thomond

Barnabas O'Brien, 6th Earl of Thomond (died November 1657), son of Donogh O'Brien, 4th Earl of Thomond; succeeded his brother as earl, 1639; was lord-lieutenant of Clare, 1640–1: had his rents seized, 1644; admitted a parliamentary garrison to Bunratty Castle and went to England: joined Charles I; successfully petitioned parliament for £2,000 spent in the parliamentary cause.

Barnabas entered the Irish House of Commons in 1613 as member for Coleraine. In 1634 he was returned for Clare as colleague of his uncle, Daniel O'Brien, afterwards 1st Viscount Clare; but, being compelled to go to England for a time, a writ was issued for a fresh election.

In 1639 Barnabas succeeded his brother Henry as sixth earl of Thomond, and applied for the governorship of Clare, which Thomas Wentworth, Earl of Strafford refused him on the ground that his conduct differed entirely from that of his brother, and that he deserved nothing. Nevertheless, he was made Lord-lieutenant and Custos Rotulorum in 1640–1. When the Irish Rebellion of 1641 broke out he attempted to maintain neutrality, in spite of the support given by his kinsmen to the confederation, and did not sign the oath of association in 1641.

Thomond lived quietly on his lands in Clare, and was in frequent communication with James Butler, 1st Duke of Ormonde. In 1644 the council of the confederation forbade Thomond's agents to collect his rents, and even formed a scheme for seizing his chief stronghold at Bunratty, which his uncle, Sir Daniel O'Brien, was appointed to carry out. Thereupon Thomond, finding that no troops were forthcoming wherewith to defend Bunratty Castle, entered into negotiations with the parliamentarians, in spite of the remonstrances of Edward Somerset, Earl of Glamorgan. At the instigation of his kinsman, Murrough O'Brien, 1st Earl of Inchiquin, he admitted a parliamentary garrison to the castle, and went to live in England.

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