Mac Duinnsléibe, Ruaidrí (d. 1201), son of Cú-Ulad and overking of Ulaid, belonged to the dynasty of Dál bhFiatach. His family descended from Donn-Sléibe (d. 1091), in turn a grandson of the illustrious Niall (qv) (d. 1063) son of Eochaid. Ruaidri's father, Cú-Ulad, died as overking of Ulaid in 1157; his mother was presumably Barrfhinn daughter of Gartnán – not otherwise identified – who is said to have been the mother of all Cú Ulad's children. In any event, he had at least six brothers or half-brothers, five of whom preceded him in the kingship: Áed (d. 1158), Domnall, who was banished by the leading claimant to high-kingship, Muirchertach Mac Lochlainn (qv), in 1164; Eochaid, who was treacherously blinded by the same Muirchertach in 1166; Magnus (sl. 1171); and Donn-Sléibe (sl. 1173). There was another brother, Niall, while Áine (d. 1171), wife of Murchad Ua Cerbaill (qv) and queen-consort of Airgialla, was perhaps a sister. There is no mention of Ruaidrí's wife, but he had at least one son, also named Ruaidrí.
Ruaidrí came to power in 1173, when his brother Donn-Sléibe, who had assassinated another sibling, Magnus, and had submitted to the English king Henry II (qv) the previous year, was killed by ecclesiastical interests for having (as is reported) profaned the relics of the north of Ireland. One of Ruaidrí's first actions as king was to blind his brother Niall, whom he presumably viewed as a threat. In 1177 Ruaidrí faced a major challenge, when the Anglo-Norman adventurer John de Courcy (qv) invaded his realm. He led an abortive attack on the ecclesiastical centre of Downpatrick, which the English had seized. Later, with the support of Cenél nÉogain (generally hostile to the Ulaid) he led another attack on the settlement, but was ignominiously routed along with his allies; many nobles were among the fallen, and the archbishop of Armagh, Gilla in Choimded Ua Caráin (qv) (d. 1180), who had accompanied the Irish forces, was abandoned to the English, who subsequently released him. The following year (1178), Ruaidrí regained the initiative when, in alliance with Ua Cerbaill, he defeated de Courcy at Glenn Righe in the plain of Conaille (south of Newry, Co. Down). Subsequently, one of his vassals, Ua Flainn of Uí Thuirtre (on the Down-Antrim border) managed to defeat de Courcy.
Despite this uplift in his fortunes, Ruaidrí had submitted to de Courcy at least by 1181; it is probable that the latter's marriage, about this time, to Affrica (qv), daughter of the king of Man and the Isles, influenced his decision to yield. Through this strategic union, his arch-rival not only gained maritime support but secured an oblique alliance with his traditional enemies, Cenél nÉogain. Later that year (or in early 1182), Ruaidrí and Ua Flainn suffered incursions by that dynasty. Submission to de Courcy notwithstanding, Ruaidrí retained his status as king of the Irish of Ulaid, although his effective authority was confined to Uí Echach Cobo, the western half of Co. Down. Clearly, he preserved a degree of political autonomy; in 1185 he was among the native rulers who submitted to Conchobar Máenmaige Ua Conchobair (qv), as the latter strove to assert his claims as high-king of the Irish. This act of defiance was most likely a reaction to the appointment by John (qv), lord of Ireland, of de Courcy as justiciar, which gave greater effect to the latter's lordship of Ulaid. The optimism generated by Ua Conchobair's meteoric career, although abruptly terminated in 1189, perhaps gave Ruaidrí the confidence to pursue ecclesiastical independence for his reduced realm which, by c.1190, had been constituted as the diocese of Dromore with one Ua Ruanada as bishop.
Some have seen in the record of Ruaidrí's activities during the 1190s evidence for an increasing tendency on his part to act as a vassal of de Courcy. He led a raid through Cenél nÉogain territory in 1195, plundering a number of churches including Donaghmore, Desertcreaght and Derryloran (all in Co. Tyrone); but exactly how this served de Courcy interests is not clear. In any event, he was defeated near Armagh a year later. It happens that his bishop, Ua Ruanada, witnessed a grant of de Courcy's c.1197, but the significance of this is difficult to gauge. Certainly he had support from colonists of Ardee when (1200) he raided Armagh (damaging the Augustinian priory in the process) and subsequently attacked Iniskeen, Co. Louth. However, it seems that, in his relationships with de Courcy, distrust remained. In 1201, Ruaidrí was killed by ‘foreigners’; AU attributes his death to ‘miracles of Sts Peter and Paul’ – patently an allusion to the damage he had caused at Armagh the previous year. According to Misc. Ir. ann., his killers were followers of de Courcy. One of his own retainers, Ua Domnalláin of Uí Thuirtre, perhaps had a role in his downfall: in 1227 his son and successor, the younger Ruaidrí, had Cú-Mara Ua Domnalláin (who had apparently enlisted for the crusades) killed in captivity ‘in revenge for his father’. Ruaidrí's line continued to rule their rump-kingdom as reges Hibernicorum Ulidiae till c.1280, when they abandoned the struggle and took up service with the Uí Néill dynasty of Cenél Conaill.