O'Donnell (Ó Domhnaill), Sir Aodh Dubh (d. 1537), lord of Tír Conaill, was born c.1471 in Co. Donegal, son of Aodh Ruadh O'Donnell (qv), lord of Tír Conaill, and his wife Fionnghuala, an O'Brien of Thomond. Aodh Dubh (‘Black Hugh’), also known in the annals as Aodh Óg (‘Young Hugh’), was the eldest of three brothers from his father's second marriage. He also had four half-brothers through his father's marriages to two other women, one of these sons, Conn, being senior to him.
Aodh Dubh is first noted in the annals in 1488 and came to prominence in 1490 when he seized his father's castle at Ballyshannon – a deliberate act against his father and his senior half-brother Conn, who was expected to succeed to the lordship. In 1496 Conn besieged Aodh Dubh in Ballyshannon castle and heavily defeated him in battle. In 1497 Aodh Ruadh abdicated as lord of Tír Conaill due to the outbreak of internecine warfare among his sons. When Conn was inaugurated Aodh Dubh rebelled against him, but after some initial success was captured and imprisoned with MacWilliam Burke in Mayo. However, Conn was killed by O'Néill the same year; Aodh Dubh was released, and ruled Tír Conaill jointly and successfully with his father for the next eight years.
In 1504 he was present at the battle of Knockdoe, near Galway city, in the victorious army of the lord deputy, Gerald FitzGerald (qv), 8th earl of Kildare (‘Gearóid Mór’). Aodh Dubh was accompanied by his father, and their presence at this battle is explained by rivalry with Uilleag Burke (qv), lord of Clanricard, and his ally Toirdhealbhach Donn O'Brien (qv), lord of Thomond, for overlordship in north Connacht.
In 1505 Aodh Ruadh died and Aodh Dubh was inaugurated (2 August) as lord of Tír Conaill at the church of Kilmacrenan. From his seat at Donegal castle he was to dominate the north-west for the next thirty-two years. In 1507 he besieged Dungannon before making peace with O'Neill, and then travelled south to meet the lord deputy, Kildare. In this year he also tried to strengthen his position in the north-west by sending letters seeking support to James IV of Scotland. One letter (dated Donegal, 13 March 1507) survives. In it Aodh styles himself ‘O'Donnel, prince of Ulster’ (Letters of James IV, no. 89, pp. 63–4). The letters were well received by King James who wrote three letters in reply. In one of them, James calls Aodh ‘his subject O'Donnel’ (ibid., no. 104, pp. 70–71) as a result of some kind of submission by Aodh's father, performed while on a visit to the Scottish court in 1495 (A.U., 1495). In 1508 Aodh took the hostages of Fir Manach by putting a fleet of ships on Lough Erne and capturing Enniskillen castle. He then made peace with O'Neill and took the hostages of Íochtair Connacht also.
In 1510 Aodh accompanied Kildare on an expedition to Munster against their common enemy O'Brien of Thomond. Aodh distinguished himself in battle when Kildare's rearguard was ambushed by O'Brien at Monabraher, near Limerick city. However, this seems to have been a very close call for Aodh: he decided to go on a year-long pilgrimage to Rome, in thanksgiving for having come through the battle. While away on pilgrimage he left his eldest and most able son, Manus (qv), in charge of the lordship. On the way to and from Rome, Aodh spent sixteen weeks each time at Westminster at the court of Henry VIII, from whom he received a knighthood (1511).
On returning in 1512, after a short illness spent in the Pale, Aodh hired 1,500 mercenaries and declared war on O'Neill for raiding Tír Conaill in his absence. Aodh also raided Connacht till both MacWilliam and O'Neill submitted; in 1513 he unsuccessfully besieged the important merchant town of Sligo for four and a half months. In this year he also visited James IV in Scotland, where he received gifts of clothes, plate, and money, and stayed at the Scottish court for three months. The annals state that he persuaded the Scottish king not to invade Ireland: Aodh undertook instead to launch a diversionary raid in Ireland, most likely against Sligo or the northern or western marches of the Pale, to complement James IV's campaign in the north of England (which ended in the disastrous Scottish defeat at Flodden, where James was killed). A large consignment of munitions, including a cannon and a culverin, were to be sent to Aodh but were recalled from the west coast of Scotland. The lord deputy, Kildare, also died this year; and Aodh never had the same relationship with his son and successor, Gerald (qv), 9th earl (‘Gearóid Óg’).
In 1514 Aodh made peace with Art Óg O'Neill, lord of Tír Eogain, at a conference at Ardstraw. In 1515 he badly injured himself with his own spear while marshalling his army, an accident that left him permanently lame. In 1516 there was ‘great war’ between Aodh and O'Neill. However, in this year Aodh finally managed to capture Sligo town with the assistance of a cannon sent from Scotland by a French knight whom Aodh had befriended while the Frenchman was on a pilgrimage to St Patrick's purgatory on Lough Derg. In 1519 Conn Bacach O'Neill (qv), a cousin of the 9th earl of Kildare, became lord of Tír Eogain. To counter this alliance, Aodh began a policy of allying with English officials sent to govern Ireland when Kildare was in disfavour. Also, in 1520 Aodh married Margery, daughter of the important Pale magnate Sir William Darcy (qv), an enemy of Kildare.
In 1522 a major war broke out between Aodh and a vast coalition led by Conn Bacach O'Neill, which included forces from all Ulster outside Tír Conaill, much of south Connacht and north Munster, and a force of Leinster mercenaries sent by the earl of Kildare. Most of the lords of Íochtair Connacht also defected from Aodh. However, in a brilliantly executed night attack, he stormed Con Bacach's camp at Knockavoe, near Strabane, and routed his army before marching into Connacht and forcing the southern coalition's army into a humiliating retreat from Sligo. In 1523 Aodh sent his son Manus into the highlands and islands of Scotland to recruit mercenaries, who duly arrived in 1524 just in time to overawe an expedition by Kildare, which reached Lifford but then withdrew. In 1525 Aodh went to Dublin to consult with Kildare, and in 1526 sent Manus in his place; however, no agreement was reached. In this year Aodh also put down a major revolt against his overlordship in Íochtair Connacht, defeating – in a major battle fought at the ford of Ballydrihid – an army that was besieging Sligo. Finally, in 1527 Manus managed to broker a peace between Aodh and Conn Bacach.
In 1530 Aodh hosted a chapter of the Franciscan Observantines at Donegal, and in 1531 sent ambassadors to sign an indenture with the lord deputy, Sir William Skeffington (qv), at Drogheda. In this year also, after a remarkably long period of internal stability, civil war broke out in Tír Conaill between Aodh and his favoured son, Manus. In 1532 Aodh visited Skeffington, but in 1533 he lost Sligo, which he had held for seventeen years. In 1535 he sent his wife, the ‘daughter of McNamee', to Skeffington to obtain English troops in order to crush Manus and retake Sligo. However, the lord deputy died before any assistance was received. In 1536 all Íochtair Connacht rebelled against Aodh.
Aodh died in the monastery of Donegal on 5 July 1537, wearing the robes of a Franciscan Observantine, and was buried in the monastery. The annals recognise him as lord of Tír Conaill, Fir Manach, and Íochtair Connacht. They also state that he obtained rent and hostages from territories in Roscommon, Mayo, Derry, and Antrim. In a contemporary O'Donnell genealogical tract Aodh is called ‘ri Leithe Cuinn’ (‘Craebhscaoileadh Cloinne Dalaigh', no. 52, p. 381), a traditional title for the king of the northern half of Ireland, much of which he did indeed dominate.
According to the tract, Aodh Dubh was married four times: first to the daughter of O'Boyle, secondly to the daughter of O'Brien, thirdly to the daughter of O'Connor, and fourthly to Sadhb, daughter of O'Neill. However, it is clear that he had a number of other relationships: Margery Darcy and Máire McNamee are recorded in other sources as also being his wives. Also, the mother of Manus, his eldest son, is not recorded. In all Aodh Dubh had fourteen sons, of whom Manus was by far the most prominent. However, another son, also called Hugh McHugh Dubh (qv) (d. 1618), was prominent in Tír Conaill during the nine years war. The name of only one daughter of Aodh Dubh – Rois – has been recorded.