INCHIQUIN, MURROUGH O'BRIEN, 1ST EARL OF (c. 1614-1674), Irish soldier and statesman, was the son of Der mod O'Brien, 5th Baron Inchiquin (d. 1624). He belonged to a great family which traced its descent to Brian Boroimhe, king of Ireland, members of which were always to the forefront in Irish public life. The first baron of Inchiquin was another Mur rough O'Brien (d. 1551) who, after having made his submission to Henry VIII., was created baron of Inchiquin and earl of Thomond in 1543. When Murrough died in November 1551 his earldom passed to his nephew Donogh, son of Conor O'Brien (d. the last independent prince of Thomond (see THOMOND, EARLS oF), leaving only his barony to be inherited by his son Dermod (d. 1557), the ancestor of the later barons of Inchiquin.
Murrough O'Brien, who became 6th baron of Inchiquin in 1624, took an active part in suppressing the Irish rebellion which broke out in 1643, and during the Civil War the English parlia ment made him president of Munster. Early in 1648, however, he declared for Charles I., and for about two years he sought to uphold the royalist cause in Ireland. He then emigrated. In 1654 Charles II. made him an earl. He died on Sept. 9, 1674.
His SOn, WILLIAM, THE 2ND EARL (C. 1638-1692), served under his father in France and Spain, and for six years was governor of Tangier. He was a partisan of William III. in Ireland, and in 1690 he became governor of Jamaica where he died in January 1692. In 1800 his descendant Murrough, the 5th earl (d. 18o8), was created marquess of Thomond, but on the death of James, the 3rd marquess, in July 1855 both the marquessate and the earldom became extinct.