Michael James Robert Dillon (2 October 1798 – 15 May 1850) was the 12th and last Earl of Roscommon.
Michael Dillon senior had been a captain in the Dublin Militia and he was killed at the Battle of New Ross, opposing the Irish Rebellion against British rule.
Michael spent 10 years working to prove his claim to the title[3] until 1828 when the United Kingdom House of Lords decided that he was the rightful heir to the Earldom and he became the twelfth Earl.
As part of its deliberations the Lords decided against Francis Stephen Dillon, an inmate of a debtors' prison who dubiously claimed descent from the third son of the first Earl.
They had a single child, a son named James who was born in 1831 but died the same year.