O'Neill, Owen Roe, 1590?–1649, Irish chieftain. Nephew of Hugh O'Neill, 2d earl of Tyrone, he left Ireland after the "flight of the earls" in 1607 and spent 30 years in the Spanish army, serving notably at Arras (1640). He returned to Ireland in 1642, superseded his kinsman Sir Phelim O'Neill as leader of the O'Neill clan, and for the next seven years led the Roman Catholic faction in the intermittently successful rebellion against English authority. O'Neill's death removed the only Irish general who might have been capable of resisting Oliver Cromwell.
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