Earl of Roscommon was a title in the Peerage of Ireland

Peerage of Ireland

The Peerage of Ireland is the term used for those titles of nobility created by the English and later British monarchs of Ireland in their capacity as Lord or King of Ireland. The creation of such titles came to an end in the 19th century. The ranks of the Irish peerage are Duke, Marquess, Earl,...

. It was created on 5 August 1622 for James Dillon, 1st Baron Dillon. He had already been created Baron Dillon on 24 January 1619, also in the Peerage of Ireland. The fourth Earl was a courtier, poet and critic. The titles became dormant on the death of the eleventh Earl in 1816. However, in 1828 the House of Lords

House of Lords

The House of Lords is the upper house of the Parliament of the United Kingdom. Like the House of Commons, it meets in the Palace of Westminster....

 decided that the rightful heir to the peerages was Michael Dillon, who became the twelfth Earl. The House of Lords Lords decided against Francis Stephen Dillon, a rival claimant. The titles became extinct on the death of the twelfth Earl on 15 May 1850.

The Viscounts Dillon

Viscount Dillon

Viscount Dillon, of Costello-Gallen in the County of Mayo, is a title in the Peerage of Ireland. It was created in 1622 for Theobald Dillon, Lord President of Connaught. The Dillons were an Hiberno-Norman landlord family from the 13th century in a part of County Westmeath was called 'Dillon's...

 and Barons Clonbrock

Baron Clonbrock

Baron Clonbrock, of Clonbrock in the County of Galway, was a title in the Peerage of Ireland. It was created on 3 June 1790 for Robert Dillon, who had earlier represented Lanesborough in the Irish House of Commons. His grandson, the third Baron, sat in the House of Lords as an Irish Representative...

 were members of other branches of the Dillon family.They were a long-established Anglo-Norman family who were recorded in Ireland from about 1185, and held substantial lands in Meath, Westmeath, Longford and Roscommon. Sir James Dillon ( died 1507 ) great-grandfather of the first Earl was a distinguished judge, as were several of his descendants.

Earls of Roscommon (1622)

• James Dillon, 1st Earl of Roscommon (d. 1642)
• Robert Dillon, 2nd Earl of Roscommon (d. 1642)
• James Dillon, 3rd Earl of Roscommon
  James Dillon, 3rd Earl of Roscommon
  James Dillon, 3rd Earl of Roscommon was one of the ten named in Act for the Settlement of Ireland 1652 as leaders of the Royalist forces in Ireland. He was a Protestant nobleman, married to Elizabeth Wentworth, one of the sisters of Thomas Wentworth, 1st Earl of Strafford. Wentworth Dillon was...
  
   (c. 1605–1649)
• Wentworth Dillon, 4th Earl of Roscommon
  Wentworth Dillon, 4th Earl of Roscommon
  Wentworth Dillon, 4th Earl of Roscommon , was an English poet.-Background and education:Dillon was born in Ireland about 1630...
  
  (c. 1630–1685)
• Carey Dillon, 5th Earl of Roscommon (1627–1689)
• Robert Dillon, 6th Earl of Roscommon (d. 1715)
• Robert Dillon, 7th Earl of Roscommon (d. 1721)
• James Dillon, 8th Earl of Roscommon (1702–1746)
• Robert Dillon, 9th Earl of Roscommon (d. 1770)
• John Dillon, 10th Earl of Roscommon (d. 1782)
• Patrick Dillon, 11th Earl of Roscommon (1769–1816)
• Michael James Robert Dillon, 12th Earl of Roscommon (1798–1850)