Sir James Dillon, 3rd Earl of Roscommon (c. 1605 – 1649) was an Irish magnate and politician. He was born a Catholic but converted at a young age to the Church of Ireland. He supported Strafford during his term as governor of Ireland. In the Confederate Wars and the Cromwellian conquest he was a royalist. He died in 1649, but was nevertheless included as the fifth on the list of people that were excluded from pardon in Cromwell's 1652 Act of Settlement.
| Family tree |
| James Dillon with wife, parents, and other selected relatives. |
| | | James 1st Earl d. 1641 | | Eleanor Barnewall d. 1628 | | |
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| Margaret Barry | | Robert 2nd Earl d. 1642 | | Ann Strode | | | | |
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James 3rd Earl c. 1605 – 1649 | | Elizabeth Wentworth | | Carey 5th Earl 1627–1689 | | Katherine Werden | | | | |
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Frances Boyle | | Wentworth 4th Earl 1637–1685 | | Isabella Boynton; | | Robert 6th Earl d. 1715 | | |
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| | | | Robert 7th Earl d. 1721 | | Angel Ingoldsby; | | James 8th Earl d. 1746 unmarried | |
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