MacDonnell (Nic Dhomhnaill), Fiona (Fionnghuala) (‘Iníon Dubh’) (d. 1611?), lady of Tír Conaill (Tyrconnell), was daughter of James MacDonnell (qv), lord of the Western Isles of Scotland, and his wife Lady Agnes Campbell (qv), and was a woman of outstanding political and diplomatic ability. Very little is known of her youth, but she received a good education and attended the court of Mary, queen of Scots. Against a background of turmoil, she emerged as a key player in her father's plans for Ulster. The campaigns of the Scottish kings had curtailed the territorial and political ambit of the MacDonnell lords of the Isles throughout the sixteenth century, and consequently their military might was directed towards colonising the northern coast of Ulster, particularly the Antrim glens. This caused chaos within the neighbouring O'Neill lordship of Clann Aodha Buidhe (Clandeboye) and considerable problems for the great O'Neill dynasty of Tír Eóghain (Tyrone) from the second quarter of the sixteenth century. On the death of her father (1567), Turlough Luineach O'Neill (qv), lord of Tyrone, offered an alliance to the MacDonnells by asking for the hand of Fiona or her mother in November 1567. In April 1568 the MacDonnells decided that Agnes should marry O'Neill, while Fiona would marry Sir Aodh mac Maghnusa O'Donnell (qv), lord of Tyrconnell (d. 1600). This alliance proved advantageous for Aodh in his struggles against both the English government who sought to curtail his power in Connacht, and the ambitions of his nephews, the sons of An Calbhach O'Donnell (qv) (d. 1566). From the early 1570s Fiona had a deciding influence in his responses to these threats, and regularly travelled to Scotland to enlist the help of her kinsmen to buttress Aodh's tenuous position. In March 1572 government officials noted her growing power over her husband and believed that she persuaded him to maintain his alliance with her stepfather, O'Neill. Despite her machinations and imported military muscle, Aodh's fortunes continued to falter and his influence in Connacht and Fermanagh was lost by the close of the 1570s.
With rebellion brewing, both O'Neill and Aodh dispatched their wives to Scotland in May 1580 to obtain mercenaries. The arrival of 2,000 Scots in Lough Foyle (August 1580) was directly attributed to their efforts and prompted English fears that the women and Sorley Boy MacDonnell (qv) were intent on transforming Ulster into a new Scotland. By 1581 the alliance with O'Neill was broken, and Aodh's fortunes were so low that he asked for English protection from his former ally. This was to no avail, and defeat quickly followed. Despite a victory over O'Neill (June 1583), the O'Donnell lordship verged on collapse as a result of the successes of An Calbhach's sons, the policies of the English government, and Aodh's poor health. In July 1587 their military weakness was obvious when Aodh accepted the imposition of English troops on his territory. However, the kidnapping and imprisonment by the English (September 1587) of their eldest son, Aodh Ruadh (‘Red’ Hugh) O'Donnell (qv) (d. 1602), was the final straw for Fiona. Realising that collapse was imminent, she moved decisively against her husband's enemies. With the help of her Scottish kinsmen, she had her principal enemy Aodh O'Gallagher, natural son of An Calbhach, killed in May 1588. This success was followed up by a victory with the aid of Hugh O'Neill (qv), 2nd earl of Tyrone, over Turlough Luineach that year. When an English garrison arrived to occupy Donegal castle in February 1589, they found it ablaze on Fiona's orders, and that she had gone to Scotland for more troops. On her return, a fresh challenger awaited her in the person of Aodh's natural son Domhnall. He attempted to seize power in 1590, but her troops killed the pretender in battle at Doire Leathan to the west of Glencolumkille on 14 September 1590. When Aodh Ruadh escaped to Tír Conaill (1592), she attended his inauguration in the knowledge she had succeeded against all the odds.
From the evidence, Aodh Ruadh clearly appreciated his mother's talents as a diplomat. In September 1597 he sent Fiona to thwart the desire of her brother Angus for revenge on Tyrone after the latter had jilted his daughter and married Caitríona Magennis. During 1599 she bought arms and recruited mercenaries for the cause of Tyrone and Aodh Ruadh before nursing her husband till his death in 1600. Her ability was again highlighted through her appointment as governor of Sligo castle by her son in June 1601. Unfortunately for her cause, she was captured with her daughter in Collooney castle in the eastern foothills of the Curlew mountains by Sir Henry Docwra (qv) in October 1601. After the submission (December 1602) of her second son Ruaidhrí O'Donnell (qv), later 1st earl of Tyrconnell, she was released and seemingly retired to her town of McGwyvelin beside Lough Foyle. In 1608 she accused Sir Niall Garvach O'Donnell (qv) of instigating the rebellion of Sir Cahir O'Doherty (qv) in April that year. This and other evidence proved decisive and Sir Niall was conveyed to the Tower of London in 1609, dying there in 1626. On 20 June 1609 it was decided that she would receive land in the plantation of Ulster, and it was in this context that she was last mentioned in May 1611, probably dying shortly afterwards.
Fiona (‘Iníon Dubh’) was one of the most remarkable Gaelic women thrown up by the turmoil of the sixteenth century. She stands alongside other Gaelic women such as Rose O'Toole (qv) and Grainne O'Malley (qv) in terms of political ability and skill. She had four sons and three daughters with her husband, Aodh.