O'Toole (Ó Tuathail), Toirdhealbhach (d. 1542), son of Art O'Toole, lord of the O'Tooles (his mother is unknown), was a powerful Irish lord in Leinster in the aftermath of the Kildare rebellion. His father was a client of the FitzGerald earls of Kildare. After 1516 the rival O'Tooles of Imaal became steadily more restless with the Kildare overlordship and attacked their clients, killing Art in 1517. This led to a considerable period of O'Toole in-fighting, and eventually to Toirdhealbhach's emergence as overlord c.1519. From the beginning he proved a shrewd politician and equally adroit diplomat, marrying a daughter of Muircheartach MacMurrough (qv) (d. 1547), lord of the MacMurrough Kavanaghs. Toirdhealbhach's first major challenge came after the arrival in Dublin (23 May 1520) of Thomas Howard (qv), earl of Surrey and lord lieutenant of Ireland. Perhaps unsure of his dynastic position, Toirdhealbhach made sure to curry favour with him. On the other hand, it suited him to develop options in the absence in England of Gerald FitzGerald (qv), 9th earl of Kildare. However, after Kildare's return to Ireland in January 1523, Toirdhealbhach was quickly back on side, accepting his gifts of horses.
Wicklow's political landscape was transformed by the murder of Robert Talbot by James FitzGerald (d. 1537) during the Christmas festivities of 1523. This enraged Sir Piers Butler (qv), the disputed earl of Ormond. Butler forces marched into Wicklow, expelling James and leading to the destabilisation of Kildare's eastern frontier. The Butler intervention also caused Toirdhealbhach to review his allegiances. After 1526 the Kildares gradually weakened, encouraging the O'Tooles to increasingly raid their earldom. On his return from England in 1529 Kildare brought Toirdhealbhach to heel after a massive campaign. Toirdhealbhach was biding his time to shake off the FitzGerald overlordship, reflecting popular sentiments among the neighbouring O'Byrnes. Their chance came in 1532. Throughout that May, Edmund O'Byrne (fl. 1540) subjected Kildare's clients to a regime of nightly terror, while in west Wicklow Toirdhealbhach's brother Art Óg O'Toole (d. 1546) publicly mocked Kildare's faltering overlordship, and burned Donard that year. But the news of the shooting of Kildare during his siege of Birr castle in winter 1532–3 cannot be overestimated in its effect on the Irish nobility of east Leinster. In 1533 the O'Tooles routed Kildare's brothers, while Edmund O'Byrne exposed Kildare's inability to defend the Pale by audaciously releasing prisoners from Dublin castle, and generally terrifying the citizens during his rampage. But it was the denunciation of Henry VIII on 11 June 1534 by Thomas FitzGerald (qv) (d. 1537), baron of Offaly, that proved Toirdhealbhach's great opportunity. Along with the O'Byrnes, Toirdhealbhach joined the forces of Sir William Skeffington (qv), earning his praise for their persecution of Kildare forces in March 1535.
Toirdhealbhach's subsequent rise to prominence among the Leinster nobility was a completely unexpected result of the Kildare collapse. Toirdhealbhach was eager to establish his dominance over all the O'Tooles and sought to create alliances with the O'Byrne lords of Glenmalure, the Kavanaghs of Garryhill, and the Art Boy Kavanaghs. He and his allies were determined to eradicate any form of restraint already existent within the Leinster mountains, first unravelling the Kildare conquest of O'Toole's Country. Thus, from the middle of the 1530s to Toirdhealbhach's submission in November 1540, this nexus was in intermittent conflict with the Dublin government. In these years the O'Tooles waxed strong, capturing and destroying the former Kildare castle of Powerscourt. Even though he was later a member of the Geraldine League, Toirdhealbhach steadfastly sought permanent confirmation of his gains throughout protracted negotiations with the FitzGeralds and the government. An example of these changed circumstances can be seen in May 1538, when Toirdhealbhach defeated John Kelway, constable of Rathmore, and a large force of Co. Kildare gentlemen at Three Castles near Blessington, killing the constable and sixty of the gentlemen.
During the lord deputyship of Lord Leonard Grey (qv), several expeditions were led against Toirdhealbhach. In December 1537 Toirdhealbhach agreed to peace for three years, promising to contribute to government hostings. In return he was to enjoy the lands his father held before the Kildare conquest and was not to aid any FitzGerald rebels. Clearly Toirdhealbhach was also on good terms with the Butlers, as Sir Piers Butler, now earl of Ossory, and his son, Lord James Butler (qv) (d. 1546), acted as sureties to the agreement. Peace did not last, pushing the O'Tooles back into the FitzGerald camp. During 1538 the English learned that the Kildare heir, Gerald FitzGerald (qv) (d. 1585), accepted from Art Óg gifts of a saffron shirt, money, and an English cloak edged with silk, at the Donegal castle of Manus O'Donnell (qv). Moreover, the confession of Conchobhar Mór O'Connor, Grey's servant, reveals that the O'Toole brothers obtained a promise of Powerscourt and Fassaroe from Gerald. Consequently, Grey led a campaign into the mountains against them and the O'Byrnes of Glenmalure during May 1539.
In April 1540 Grey was recalled to England after the fall of Sir Thomas Cromwell, his patron. In response to Grey's departure Brian O'Connor Faly (qv), along with Giolla Pádraig O'More (qv) and Toirdhealbhach, burned part of the Pale. Government concern increased as O'Connor Faly continued burning in Kildare throughout early May, while Tadhg O'Byrne (qv) foiled a huge O'Toole raid on the Pale by warning the Palesmen. Significantly, a government army was dispatched during the middle of June to O'Toole's Country. There it was confronted by the forces of Toirdhealbhach, the Kavanaghs of Garryhill, and the O'Byrnes of Glenmalure. Because of the strength of the Irish as well as a lack of supplies, the government made a peace of six weeks. A more illustrative example of the extent of Irish coordination came in July. Then James Butler, now earl of Ormond, invaded Idrone, forcing Toirdhealbhach to hasten to the aid of the Kavanaghs of Garryhill. However, the size of Ormond's army convinced Toirdhealbhach that a truce was a better option.
In September 1540 the O'Toole truce expired. That month the army of the lord deputy, Sir Anthony St Leger (qv), secured the submissions of most of the O'Byrnes and MacMurrough Kavanaghs, but the O'Tooles remained elusive, making St Leger more determined to subdue them. To that end he sought money from England to rebuild two castles facing the mountains of the O'Tooles. After a four-week campaign in November, St Leger and Ormond cornered Toirdhealbhach. There Ormond convinced the tired O'Toole leader to come to terms. As the price of his obedience Toirdhealbhach requested the formal recognition of his claims, demanding that the ancestral lands of the O'Tooles be granted to him and his brother, Art Óg. After Toirdhealbhach's submission, St Leger dispatched him to court, where he made his submission to Henry VIII in early 1541. In return Henry confirmed Toirdhealbhach's tenurial rights and those of his brother. Thus, O'Toole claims to the castles of Castlekevin and Powerscourt and to ancestral lands lying in north and central Wicklow were legitimised. Henry's confirmation of the articles of the St Leger–O'Toole agreement greatly ameliorated the grievances of the Irish of the Wicklow highlands. However, peace was short-lived, as strife among the O'Tooles again destabilised the Irish of East Leinster.
In early 1542 Toirdhealbhach attempted to exert his overlordship over his cousin Toirdhealbhach mac Seaáin O'Toole of Imaal, but he was killed by his rival in a surprise morning attack on his encampment. Toirdhealbhach's death destroyed the equilibrium he had been building for the best part of a decade among the Irish of the mountains. Indeed, Toirdhealbhach's death and the later killing of his heir, Toirdhealbhach Óg, by Toirdhealbhach mac Seaáin before May 1543 opened up considerable opportunities for the O'Byrnes of Glenmalure. After 1542 they positioned themselves to fill Toirdhealbhach's leadership role among the Irish of the Leinster mountains, leading them into direct conflict with the Butlers of Ormond and later the government. Their rise was also helped by the death of Art Óg about summer 1546 at his castle at Castlekevin, leaving them alone to pose as the leaders of the mountain lords.