Niall Garve O'Donnell

Niall Garve O'Donnell (Irish: Niall Garbh Ó Domhnaill; c. 1569 – 1626) was an Irish nobleman and soldier who claimed the lordship of Tyrconnell, alternately a rebel against and ally of English rule in Ireland. He is best known for siding with the English against his kinsman Hugh Roe O'Donnell during the Nine Years' War.

Although Niall's paternal grandfather was O'Donnell clan chief and Lord of Tyrconnell, his own father was passed over in favour of his half-uncle Hugh McManus O'Donnell. After a violent succession conflict, Hugh McManus's son Hugh Roe—Niall's younger cousin by two years—succeeded to the lordship in 1592. A long lasting bitterness ensued between the two cousins.

Niall initially fought for Hugh Roe and the Irish confederacy, but in 1600 he entered secret negotiations with leading royal soldier Henry Docwra. The English government hoped to harness Niall's feud against Hugh Roe and promised him the lordship of Tyrconnell for his military assistance. Niall defected in October bringing many followers with him.

Niall's skills in guerrilla warfare emboldened the English troops and allowed Docwra to significantly weaken Irish forces in Ulster. However, Niall's request that the English government not interfere with his promised lordship was incompatible with the Crown's plan for Ireland. After the war ended, Niall was not granted the lands or titles he was promised. In early 1608 Niall instigated fellow spurned loyalist Cahir O'Doherty to launch a rebellion in Derry, but he was quickly implicated and put on trial. Faced with a sympathetic jury that would almost certainly acquit, the government sent Niall to the Tower of London in 1609, where he remained until his death seventeen years later.

The O'Donel baronets of Newport House, County Mayo, were descended from Niall's grandson Rory.