Tyrconnel, Rory O'Donnell, earl of, 1575–1608, Irish chieftain; brother of Hugh Roe O'Donnell, lord of Tyrconnel, whom he succeeded as chief of the clan in 1602. After the rebellion in which his brother had been a leading figure, Rory went to London (1603) to submit to James I. He was knighted, created earl, and made sheriff of Donegal. However, he soon engaged in a conspiracy with Spain to seize Dublin Castle and the government and to start a general uprising. His flight (1607) with Hugh O'Neill, 2d earl of Tyrone, after the discovery of the plot, signified the end of political power of the Irish tribal chieftains. He died at Rome and was posthumously attainted (1613) by the Irish Parliament.