Domnall Ua Lochlainn

Domhnall Ua Lochlainn (old spelling: Domnall Ua Lochlainn) (1048 – 10 February 1121), also known as Domhnall Mac Lochlainn (old spelling: Domnall Mac Lochlainn), claimed to be High King of Ireland.

The meaning, and even the definition, of the High Kingship of Ireland to which Domnall laid claim was far from clear in the period after the death of the last traditional Uí Néill king of Tara, Máel Sechnaill mac Domnaill of Clann Cholmáin, in 1022. Later, rival kings produced differing definitions. Domnall's legal men, for example, claimed that a High King "with opposition" was the king of a province who could lead his army throughout Ireland without defeat, and this Domnall could do. The supporters of his southern rival, Muirchertach Ua Briain of Munster, disagreed, and said a High King "without opposition" should control three great port cities of Ireland: Dublin, Waterford, and Limerick, cities over which Muirchertach exercised some control.

Regardless of legal fictions, the first king to construct something resembling an overlordship of Ireland after the death of Máel Sechnaill was Diarmait mac Maíl na mBó of the Uí Cheinnselaig. Only called King of Leinster and the Foreigners in his obituary, Diarmait was more than this, the effective ruler of much of Ireland. His son Murchad ruled Dublin, Toirdelbach Ua Briain in Munster was his client, and Niall mac Eochada of Ulster was his ally. Diarmait's career ended with his death in battle, attempting to subjugate the heirs of Máel Sechnaill, on Tuesday 7 February 1072.

Diarmait's position was quickly taken by his former puppet Toirdelbach Ua Briain. Ua Briain installed his son, Muirchertach in Dublin, and campaigned in Ulster. In Leinster and Connacht he pursued a policy of setting rival families against each other. Domnall Ua Lochlainn, on his coming to power in 1084, was left undisturbed by Ua Briain, who fell ill the following year and died in 1086, aged 77. At his death, even the partisan northern annals recognised Toirdelbach Ua Briain as king of Ireland.

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