MacLoughlin (Mac Lochlainn), Domnall (d. 1241), last of the MacLoughlin kings of Ulster, may have been a son of Muirchertach MacLoughlin (d. 1196), king of Cenél nEógain. Even during the latter's reign, MacLoughlin domination of Ulster was in doubt. The seeds of this decline in MacLoughlin fortunes originate after the fall during 1166 of Muircheartach Mac Lochlainn (qv), high-king of Ireland. After Muircheartach's death Ruaidrí Ua Conchobair (qv) (O'Connor) (Ó Conchobair) (d. 1198) divided the kingdom between the MacLoughlin successors and their rival, Áed O'Neill. In general, though, the MacLoughlin kings, based in north-western Tír Eogain, remained the dominant power there till 1196. Indeed, after 1166 they provided three consecutive kings: Máel Sechlainn, Domnall, and Muirchertach. This dominance was maintained in spite of the determined challenges of Áed O'Neill, Ruaidrí MacDonleavy (Mac Duinn Sléibe) (d. 1201) of Ulaid, and the English throughout the 1160s to the early 1190s. But the killing of Muirchertach in 1196 by the O'Kanes (Uí Catháin) brought dramatic changes. The relative weakness of the MacLoughlins in the aftermath allowed Flaithbertach O'Mulderry (Ó Máel Doraid) (1147–1196/7), king of Donegal, to briefly claim overlordship over them (1196/7). But the real danger was from the O'Neills. From southern Tír Eogain, O'Neill ambition emerged under the leadership of Áed Méith O'Neill (qv) (d. 1230), an aggressive and expansionist king. Áed Méith was determined to maintain and spread his growing influence throughout north-west Ireland, interfering regularly in Connacht and east Ulster after 1199. This meant wresting the title of king of Ailech away from his MacLoughlin rivals, resulting in bitter and bloody conflicts. The tenuous position of the O'Neill king was revealed in 1201. After his return from an unsuccessful campaign in Connacht that year, Áed Méith was deposed as king of Ailech by Conchobar Bec MacLoughlin. But MacLoughlin's death at the hands of the O'Donnells (Uí Domnaill) before the close of the year ensured Áed Méith's swift return to the kingship. Although Áed Méith faced similar challenges from Magnus and Diarmait MacLoughlin in 1201 and 1204 respectively, he retained the kingship till his own death in 1230. As regards Domnall, nothing directly is known of him till 1233, although he may be the ‘son of Mac Lochlainn’ engaged in a struggle at Derry with the O'Kanes in 1213. On the other hand, it can also be adduced that this may refer to Áed MacLoughlin, the raider of the shrine of Colum Cille (qv) in 1215. What is certain, though, is that the death of Áed Méith in 1230 signalled the end of the uneasy truce between the O'Neills and the MacLoughlins. By this time Domnall was the MacLoughlin leader and was full of ambition, paving the way for a resumption of the struggle for supremacy. Áed Méith was succeeded by his son, Domnall Ó Néill (d. 1234), as king of Ailech. Domnall MacLoughlin naturally disputed this succession and claimed the kingship for himself. In 1232, with a mixed force of Irish and English, he devastated much of Donegal and Fanad, taking hostages of the O'Boyles. This plundering forced Domnall O'Donnell (qv) (d. 1241), king of Donegal, to retaliate. His offensive against Domnall MacLoughlin and his allies reached deep into Tír Eógain to Tulach Óc, perhaps indicating that the O'Neills and Domnall were allied. Inevitably, Domnall brought the war back to the doorstep of O'Donnell, sailing with a fleet to ravage the Mevagh and Aughnish districts of Donegal successfully. By 1234 Domnall felt sufficiently confident to challenge Domnall O'Neill for the kingship, defeating and killing him that year. However, there were greater enemies than the O'Neills. In early 1238 one of Domnall's vassals from Ulaid was killed while travelling to the castle of Hugh de Lacy (qv) (d. 1243), earl of Ulster. This killing enraged Domnall and his allies, resulting in a huge outbreak of violence in Ulster. Such was the strength of the Irish that de Lacy was expelled from Ulster. However, he appealed to the justiciar, Maurice FitzGerald (qv) (d. 1257), and assembled a huge army to invade Ulster. During the harvest months of 1238 they invaded and deposed Domnall before taking the hostages of the North. In his place they gave the kingship to ‘the son of O'Neill’, perhaps Brian O'Neill (qv) (d. 1260), son of Niall Ruad O'Neill (d. 1222). According to the Annals of Clonmacnoise, Domnall (although he seems to be named as ‘Máel Sechlainn Ua Lochlainn’ in the text) was banished into Connacht. He was to have his revenge. During 1239 Domnall returned to Ulster, gathered an army, and invaded the O'Neill territories. At Carnteel (near Aughnacloy), he challenged Brian O'Neill to battle. Although the O'Neills had MacMahon (Mac Mathgamna) support, Domnall fashioned a resounding victory, killing Domnall Tamnaige O'Neill and MacMahon. After this, Domnall turned his attention to Hugh de Lacy. In a ferocious encounter Domnall expelled him from Ulster, killing his son and twenty-eight mail-shirted men. To counter Domnall's successes, Richard Tuite in 1240 was dispatched with an army to stamp him out. But Domnall proved too strong. In 1241 Brian O'Neill appealed for help to Máelsechlainn O'Donnell (qv) (slain 1247). Clearly O'Donnell had much to fear from a MacLoughlin resurgence on his borders, led by the able Domnall. O'Donnell joined Brian O'Neill and invaded the territory around Derry, plundering as they went. At the battle of Caimeirge (Cummery, in the townland of Erganagh, north of Omagh), the O'Neills and O'Donnells annihilated the forces of Domnall and his allies. The Annals of the Four Masters record the slaughter, stating that Domnall and no less than ten major leaders of the MacLoughlin dynasty fell that day. The extinguishing of Domnall's life ensured the rise of the O'Neills in Ulster and ended the prominence of the great MacLoughlin dynasty, which had supplied two high-kings of Ireland between 1080 and 1166.
D. O'Byrne, History of Queen's County (1856), 94; Ann. Clon., 233, 236, 237; AU, ii, 225, 241, 259, 289, 295, 291; AFM, iii, 81, 123, 137, 179, 265, 297, 303; Ann. Conn., 51, 69, 71, 73, 75; MacCarthy's Book, 63, 71, 77, 78, 79, 117, 119; ALC, i, 193, 195, 205, 221, 321, 349, 351; G. H. Orpen, ‘The Normans in Tir Owen and Tir Connell’, R.S.A.I.Jn., xlv (1915), 123–42; K. Simms, ‘Tír Eoghain “north of the mountain” ’, G. O'Brien (ed.), Derry and Londonderry: history and society (1999), 149–73; C. Brady, Shane Ó Néill (1996), 10; Charles Dillon and Henry A. Jefferies (ed.), Tyrone: history and society (2000)