Máel-Sechnaill (Máel-sechlainn II; Malachy Mór) (948–1022), was the son of Domnall, high-king of Ireland. He was a member of the Southern Uí Néill dynasty of Clann Cholmáin, based in the area of Westmeath. His father was the relatively insignificant Domnall Donn, described as rígdamnae (royal material, heir designate) of Tara at his death in 952. His grandfather was the powerful Donnchad Donn (qv) (d. 944) and his great-grandfather the famous Flann Sinna (qv) (d. 916), high-king. His mother was Dúnlaith, daughter of Muirchertach na Cochall Craicinn (qv) (d. 943) son of Niall Glúndub (qv) (d. 919) of the Cenél nÉogain. His half-brother was Glún Iarn (d. 989) through his mother's marriage to Amlaíb Cúarán (qv), Norse king of Dublin.
There is some uncertainty concerning Máel-Sechnaill's marriages and wives. Mór, daughter of Donnchad (d. 976) son of Cellach, king of Osraige, is described in her death notice in 986 as banrígan hÉrenn (queen of Ireland). Since the name of her husband is taken for granted, it seems reasonable to assume that she was Máel-Sechnaill's wife. This lady, Mór of Moyne in Mag Síuil, had a poem written for her on the loss of her pet goose, in which Brian Bó-rama (qv) is mentioned as king of Munster. While the poem could date to this period, it is more likely to date to a time in the eleventh century, when romantic material surrounding the heroes of Clontarf began to be written. Another Mór, daughter of Tadc (d. 956) son of Cathal (qv), king of Connacht, is also described as ‘queen of Ireland’ on her death (992); and again, since the name of her husband is not given it may be assumed that she was another of his wives. The ‘Banshenchas’ (women-lore) lists a Mór as Máel-Sechnaill's daughter, presumably called after her mother, one or other of the aforementioned women. She was mother of Cenn-Fáelad (d. 1078) son of Dúnchad Find son of Cerrán son of Dúngalach, king of Múscraige Tíre. This seemingly insignificant kingdom, occupying an area on the north-east side of Lough Derg north of the Nenagh river, was of strategic importance, acting as a spearhead into the midlands for its overlords the Dál Cais from across the Shannon, and a first line of defence for Dál Cais against attack from the north. Another wife was Máel-Muire (d. 1021), daughter of Amlaíb Cúarán. Máel-Sechnaill was also said to have been married to the famous Gormlaith (qv) (d. 1030), daughter of Murchad (d. 972) son of Find of the north Leinster dynasty of Uí Fháeláin – possibly, it has been suggested, in the 980s or 990s. She had previously been married to Amlaíb Cúarán, by whom she had a son Sitriuc Silkbeard (qv) (d. 1042), king of Dublin. Her son with Máel-Sechnaill was Conchobar (d. 1030). She was also wife of Brian Bórama. Facts about Gormlaith are coloured by the later romantic tradition in which she is enveloped, which may cast doubt on the existence either of a marriage or of a son Conchobar.
Máel-sechnaill had other sons. Donnchad, a member of Máel-Sechnaill's household nobles, was killed (1013) in north Meath in pursuit of a raiding party while drunk. In the same year Flann was killed on a raid that his father made as far as Howth. The raiding party, led by Flann, was overtaken by Sitriuc Silkbeard, king of Dublin, and Máel-Mórda (qv), king of Leinster, at Drinan near Kinsaley, Co. Dublin, and one hundred and fifty were slain. His son Congalach was killed on a raid into the territory of the Fir Chell and Éile (Offaly) in 1018. Domnall (d.1019), comarba Finnen 7 Mo-Colmóg (successor of Finnian (qv) and Mocholmóg (Colmán (qv) (d. 654)), both of whom had been head of Clonard, Co. Meath): this son had been in charge of one of the greatest churches in the midlands. Máel-Sechnaill's brother Flaithbertach died in 1014 as comarba Ciarain 7 Finnen (successor of Ciarán (qv) and Finnian), i.e. head of Clonmacnoise and Clonard. Through his family, therefore, Máel-Sechnaill had a firm grip on the two most important monastic churches in the midlands. The fate of his last two sons is known from the annals. Murchad Ruad was blinded (1039) by his nephew, Conchobar (Conchobar Ua Máelshechlainn (qv)), king of Tara 1030–73, son of Domnall (head of Clonard as mentioned above); in 1049 the same Conchobar killed his other uncle, Muirchertach, despite secular and ecclesiastical pledges.
Máel-Sechnaill became king of Mide following the death (974) of the brothers Donnchad Finn and Muirchertach, sons of Áed son of Flann Sinna. In demonstration of his new position, the following year he raided Dublin and demolished the ‘wood of the foreigners’. In the late tenth century the Northern Uí Néill king Domnall Ua Néill (qv) attempted to assert direct control over the midlands. The Dublin king Amlaíb Cúarán had ambitions in the same area and may even have had his eye on the kingship of Tara, as his killing (977) of Muirchertach and Congalach, sons of Domnall Ua Néill, might suggest. On Domnall's death in Armagh (980) Máel-Sechnaill succeeded to the high-kingship. As the new high-king, Máel-Sechnaill asserted his authority by inflicting a massive defeat on Amlaíb and his allies from the Isles in the battle of Tara (980). This battle was seen at the time as the expulsion of the power of the Norse from Ireland. This was followed up by a siege of Dublin for three days and nights in the company of Eochaid son of Ardgar king of the Ulstermen. The hostages of Ireland were released, including the king of Leinster, Domnall Cláen. More importantly, the Uí Néill lands from the Shannon to the sea were freed from taxation, and Irish captives and slaves in the lands of the Norse were allowed to come home.
In 982 Máel-Sechnaill made a raid into Dál Cais territory in Munster and cut down the tree of Mag Adair (their inauguration site, in the townland of Toonagh, parish of Clooney, Co. Clare). In 983, in the company of his stepbrother Glún Iarn, he defeated Domnall Cláen, king of Leinster, and Ímar (qv) of Waterford. In 985 he turned to the province of Connacht and reduced Mag Aí to ashes, although the Connachta came behind him and plundered his home territory around Lough Ennell. In 986 he offended Armagh by carrying off the shrine of St Patrick (qv) from Ardee as a result of the war of the sons of Cairellán, and had to pay heavy reparation. It is possible that the Ciar Caille son of Cairellán (O'Brien, Corpus, 179), king of north Brega who died in 988, otherwise unknown in the southern Uí Néill genealogies, was a northern Uí Néill intruder in this area, whom he was attempting to repulse.
In 989 Glún Iarn, king of Dublin, his stepbrother, was killed by his slave while drunk. Máel-Sechnaill laid siege to Dublin for twenty nights, cut off the water supply until the town submitted, and exacted an ounce of gold from each tenement on each Christmas night. In 990 he decisively defeated a raid by the north Munstermen and their Múscraige Tíre allies at Fardrum, approximately 4 km (2.5 miles) south-east of Athlone. In the 990s he had to put down ruthlessly opposition in his own territories. In 991 he had Donnchad of the north Brega dynasty deceitfully killed. In 993 he had the king of Luigne killed in the abbot's house in Domnach Pátraic (Donaghpatrick, between Kells and Navan). He burned Swords in 994. In 998 he killed the king of Mugdorna, and in 999 he demolished the Lia Ailbe stone pillar (possibly at Clonalvy, Co. Meath) and had it made into millstones.
In 992 Máel-Sechnaill made a successful raid into Connacht, but Brian Bórama followed this by a similar raid that went into Máel-Sechnaill's home territory, avoiding an engagement but making a demonstration of intent. In the following year Brian brought a fleet onto Lough Ree. In 994 Máel-Sechnaill burned Nenagh and plundered Munster. In 995 he made a raid on Dublin, taking the ring of Tomar and the sword of Carlus, but it was increasingly clear that an accommodation would have to be made with Brian in the south. In 997 they reached agreement at Port Dá Chaineóc, near Clonfert, to divide control of the island between them, with Máel-Sechnaill giving Brian the hostages of Leinster and the city of Dublin. In 998 they went on a joint expedition against the Dubliners and Connachta. In December 999 Brian marched on Dublin to maintain control of the Norse kingdom. On Thursday 30 December his forces were met by the Norse at Glenn Máma, a site plausibly suggested to be the gap between Kill and Rathcoole. This was a massive battle with very great casualties on both sides. Brian was victorious and entered the town on New Year's Day 1000 and sacked it. He now had a firm base on which to face Máel-Sechnaill, whose support was on the wane. Despite initial successes against Brian and the building of causeways (with the help of the Connachta) across the Shannon at Athlone and Lanesborough (1001) to control any Munster advance, Máel-Sechnaill finally had to accept the superiority of his arch-rival. He was forced to relinquish the high-kingship to Brian in 1002 but resumed the position on the latter's death at Clontarf in 1014.
Following the loss of the high-kingship Máel-Sechnaill's plight was exacerbated by a fall from his horse (1004), ‘so that he lay mortally ill’. With Máel-Sechnaill incapacitated, Brian went on circuits of Ireland demonstrating his supremacy. In 1007 Máel-Sechnaill presented the Carracán tempaill Solman (the carracan (? model) of Solomon's temple), to the church of Clonmacnoise together with a hide from every fort in Mide, possibly in thanksgiving for his recovery. The item was stolen from the altar of the great church with many other relics in 1129 but subsequently recovered. To demonstrate his return to action he held the Aonach Tailten (fair of Tailtiu; Teltown, Co. Meath) in the same year. In the years leading up to the battle of Clontarf he maintained his position within his own territories and gave support to Brian when requested, particularly in revenge for the profanation of the relics of Patrick (1013) by the Conaille (Louth). Despite confusion in the sources, it is likely that he took part in the historic battle. In the year after Clontarf he was assisted in consolidating his power by Flaithbertach Ua Néill (qv) of the North, who killed the king of Uí Moccu Uais of Meath (1017), presumably protecting his dynasty's interests. In these years he reasserted his control over Leinster and Ulster and campaigned against Osraige, while in 1019 he took the hostages of Connacht. In this way he returned to the position he held before the rise of Brian.
Máel-Sechnaill died on his home crannog of Cróinis, in the south-west corner of Lough Ennell, aged 73, on Sunday 2 September 1022. He was attended at his deathbed by the successors of Patrick, Colum Cille (qv), and Ciarán (that is, the heads of Armagh, Kells, and Clonmacnoise), eloquent testimony to the esteem in which he was widely held. In his death notice in the Annals of Ulster he is described as the ‘pillar of the dignity and nobility of the western world’, an encomium that he surely deserved.