Earl of Thomond

Earl of Thomond was an hereditary title in the Peerage of Ireland. It was created twice for the O'Brien dynasty which was an ancient Irish sept native to north Munster.

Under the Crown of Ireland Act 1542, King Henry VIII of England was created King of Ireland by the Parliament of Ireland. In consequence, all reigning monarchs and clan chiefs in Ireland were ordered to surrender their native titles in return for peerages. This surrender and regrant offer was conditional upon the adoption of Tudor customs and laws, including pledging allegiance to the Irish Crown and apostatising the Catholic faith by accepting the articles of the state established Church of Ireland.

The earldom was first created in 1543 for Murrough O'Brien. He had previously been styled King of Thomond and was descended from the Ard Ri or High King of Ireland, Brian Boru. O'Brien was also created Baron Inchiquin, on 1 July 1543. On the same day his nephew and heir, Donough O'Brien, was created Baron Ibrickane. The titles of Ibrickane and Thomond merged on the first Earl's death in 1551, and the barony of Inchiquin went to his eldest son.

The 8th Earl was created Viscount Tadcaster, in the Peerage of Great Britain, on 19 October 1714. However, when he died in 1741, the next heir would have been a descendant of Daniel O'Brien, 3rd Viscount Clare who was attainded in 1691, so the three titles became forfeit. However, Charles O'Brien, 6th Viscount Clare, a Jacobite exile used the title Earl of Thomond, as did his son, who died childless in 1774.

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