Domhnall Ua Lochlainn (old spelling: Domnall Ua Lochlainn) (1048 – 10 February 1121), also known as Domhnall Mac Lochlainn (old spelling: Domnall Mac Lochlainn),[1] was king of the Cenél Eogain, over-king of Ailech, and alleged High King of Ireland.
^Ua Lochlainn and its replacement Mac Lochlainn are surnames, from which the modern Irish surnames McLaughlin, O'Loughlin and MacLoughlin are derived. They should be distinguished from ua Lochlainn and mac Lochlainn, usually meaning grandson and son of Lochlann respectively.