Earl of Thomond
History and background 
Surrender and regrant 
In 1542 under the Crown of Ireland Act, King Henry VIII of England and France, Lord of Ireland was created King of Ireland by the Irish Parliament. In consequence, all reigning monarchs and clan chiefs in Ireland were ordered to surrender their native titles in return for peerages. The regrant of title was also conditional upon the adoption of Tudor customs and laws, including pledging allegiance to the Irish Crown, and the acceptance of the articles and leadership of the new Anglican Church.
First creation 
The first creation of the Earldom of Thomond took place in 1543 for Murrough O'Brien, previously King of Thomond, who 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.
Forfeit of title 
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.
Second creation 
The second creation was for Percy Wyndham-O'Brien, who on 11 December 1756, was created Earl of Thomond and Baron Ibracken. On his death in 1774 both his titles became extinct.
Earls of Thomond (1543) 
- Murrough O'Brien, 1st Earl of Thomond (d. 1551)
- Donough O'Brien, 2nd Earl of Thomond (d. 1553) – created Baron Ibrickane in 1543.
- Connor O'Brien, 3rd Earl of Thomond (c.1535–1581)
- Donogh O'Brien, 4th Earl of Thomond (d. 1624)
- Henry O'Brien, 5th Earl of Thomond (c.1588–1639)
- Barnabas O'Brien, 6th Earl of Thomond (c.1590–1657)
- Henry O'Brien, 7th Earl of Thomond (c. 1620–1691)
- Henry O'Brien, 8th Earl of Thomond (1688–1741), grandson of the 7th Earl. All titles forfeit on his death.
- Charles O'Brien, 6th Viscount Clare, titular 9th Earl of Thomond (1699-1761)
- Charles O'Brien, 7th Viscount Clare, titluar 10th Earl of Thomond (died 1774)
Earls of Thomond (1756) 
- Percy Wyndham-O'Brien, 1st Earl of Thomond (c. 1723–1774)
See also 
- Cokayne, George Edward, ed. (1896). Complete peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, extant, extinct or dormant (S to T) 7 (1st ed.). London: George Bell & Sons. p. 391–394. Retrieved 28 December 2011.