Sir James Dillon, 3rd Earl of Roscommon ( – 1649) was an Irish magnate and politician. He was born a Catholic but converted as 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.