Rosa O'Neill (c.1588–1660) was a member of the O'Doherty family of County Donegal who lived during the late Tudor and Stuart eras.
Born Rosa O'Doherty, Rosa was the daughter of Sir John O'Doherty, and the younger sister of Sir Cahir O'Doherty. The O'Doherty's were the traditional rulers of Inishowen. Sir Cahir fought on the Crown's side during Tyrone's Rebellion (1594-1603). In 1608, angered at his treatment by local officials, he launched O'Doherty's Rebellion by burning Derry. Sir Cahir was defeated and killed at the Battle of Kilmacrennan, and Inishowen was confiscated from the family.
Rosa had earlier been married to Cathbarr O'Donnell, the younger brother of Rory O'Donnell, 1st Earl of Tyrconnell. Both Cathbarr and Rosa accompanied Rory to Continental Europe during the 1607 Flight of the Earls. Her husband died of fever in Italy the following year, leaving Rosa widow at the age of twenty.
She remarried in 1613-14 to Owen Roe O'Neill, an Irish officer serving in the Spanish army who she met in Flanders.
In 1642 when Owen Roe returned to Ireland to serve the Irish Confederacy during the War of Three Kingdoms, Rosa accompanied him. She arrived after her husband, landing at Wexford with supplies and reinforcements for her husband's Ulster Army. Owen Roe became a leading figure of the Irish Confederacy, enjoying mixed fortunes but winning a notable success against Scottish forces at the Battle of Benburb in 1646.