The Mac Lochlainn (Irish pronunciation: [mˠək ˈl̪ˠɔxl̪ˠən̠ʲ]) were a leading branch of the Cenél nEógain and during the early medieval period, the most powerful clan in the Northern Uí Néill.
[6] The surnames themselves formed not as a result of Lochlann's prominence, but as a consequence of the remarkable success of his grandson, Domnall Ua Lochlainn (died 1121).
In 1215, Áed Mac Lochlainn was slain battling the Uí Catháin, a rising kindred in what is today County Londonderry.
The virtual extirpation of the Meic Lochlainn leadership at this defeat meant that the family was finally eclipsed by the rival Ua Néill kindred.
Although there are later recorded Meic Lochlainn chieftains, the diminished family lost the lordship of their Inishowen homeland, which in turn came to be possessed by the Ua Dochartaigh kindred.