Ulaid also refers to a people of early Ireland, and it is from them that the province derives its name. Some of the dynasties within the over-kingdom claimed descent from the Ulaid, whilst others are cited as being of Cruithin descent. In historical documents, the term Ulaid was used to refer to the population-group, of which the Dál Fiatach was the ruling dynasty. As such the title Rí Ulad held two meanings: over-king of Ulaid; and king of the Ulaid, as in the Dál Fiatach.
The Ulaid feature prominently in the Ulster Cycle of Irish mythology. According to legend, the ancient territory of Ulaid spanned the whole of the modern province of Ulster, excluding County Cavan, but including County Louth. Its southern border was said to stretch from the River Drowes in the west to the River Boyne in the east. At the onset of the historic period of Irish history in the 6th century, the territory of Ulaid was largely confined to east of the River Bann, as it is said to have lost land to the Airgíalla and the Northern Uí Néill. Ulaid ceased to exist after its conquest in the late 12th century by the Anglo-Norman knight John de Courcy, and was replaced with the Earldom of Ulster.
An individual from Ulaid was known in Irish as an Ultach, the nominative plural being Ultaigh. This name lives on in the surname McAnulty or McNulty, from Mac an Ultaigh ("son of the Ulsterman").
Ulaid is a plural noun and originated as an ethnonym, however Irish nomenclature followed a pattern where the names of population-groups and apical ancestor figures became more and more associated with geographical areas even when the ruling dynasty had no links to that figure, and this was the case with the Ulaid. Ulaid was also known as Cóiced Ulad, the "Fifth of Ulster", and was one of the legendary five provinces of Ireland. After the subsequent loss of territory to the Airgíalla and Northern Uí Néill, the eastern remnant of the province that formed medieval Ulaid was alternatively known as in Chóicid, in reference to the unconquered part of Cóiced Ulad.
The Ulaid are probably the Ούολουντοι (Uolunti or Volunti) mentioned in Ptolemy's 2nd century Geographia. This may be a corruption of Ούλουτοι (Uluti). The name is probably derived from the Gaelic ul, meaning "beard". The late 7th-century writer, Muirchú, spells Ulaid as Ulothi in his work the Life of Patrick.