Earl of Roscommon

Earl of Roscommon was a title in the Peerage of Ireland. 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 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 and Barons Clonbrock 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.