Barnabas O'Brien, 6th Earl of Thomond (1590-November 1657), was Chief of Clan O'Brien and son of Donogh O'Brien, 4th Earl of Thomond. He succeeded his elder brother as earl in 1639 and was made lord-lieutenant of Co. Clare in 1640–41. He 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.[1]