Eilne, also spelt as Eilni, alias Mag nEilne, was a medieval Irish Cruthin petty-kingdom in the over-kingdom of Ulaid. It lay between the River Bann and River Bush,^[1] and was centered on Magh nEilne, the "plain of Eilne", spanning north-east County Londonderry and north-west County Antrim, in present-day Northern Ireland. Eilne may represent the name of an original population grouping, though even in the Old Irish period who they were was forgotten.^[2]

The end result of conquest first by the Dál nAraidi and then the Uí Tuirtri resulted in Eilne later becoming known simply as An Tuaiscert, which survived into the late medieval period as the name of a medieval deanery and the Anglo-Norman cantred of Twescard.^[3]

This section needs additional citations for verification. (August 2022)

In 563 the battle of Móin Daire Lothair (modern-day Moneymore) took place between an alliance of Cruthin kings and the Northern Uí Néill.^[4] The Cruthin suffered a devastating defeat and lost the territories of Ard Eólairg (Magilligan peninsula) and the Lee, which both lay west of the River Bann, with the Northern Uí Néill settling their Airgíalla allies in Eilne.^[4] The Cruthin afterwards consolidated themselves in the Dál nAraidi.^[4]

In the mid-7th century the Dál nAraidi of Magh Line conquered Eilne to their north-west and one of their dynasty seems to have settled there, with this branch eventually being known as the Dál nAraidi in Tuaiscirt.^[3][5]

In 681, Dungal Eilni, king of the Cruthin, who was of the Dál nAraidi in Tuaiscirt was killed at Dún Ceithern (modern-day Giant's Sconce in parish of Dunboe, west of River Bann) along with the king of Cianachta Glenn Geimin by Máel Dúin mac Máele Fithrich of the Cenél Meic Ercae of Cenél nEógain.^[4][6][7]

Cathussach mac Ailello, king of Eilne and Dál nAraidi, and claimed as having ruled the over-kingdom of Ulaid for sixteen years, was killed at Ráith Beithech (Rathveagh, County Antrim) in 749.^[8]

At the end of the 8th-century, the Airgíallan Uí Tuirtri, whose kingdom lay west of the River Bann, started to migrate into Eilne due to pressure from the encroaching Cenél nEógain.^[1]

Eochaid mac Bressal, who died in 832, was the last known king of the Dál nAraidi in Tuaiscirt to hold the over-kingship of the Dál nAraidi.^[3]

By the 10th-century, Eilne was under the control of the Uí Tuirtri who had also moved their client kingdom of Fir Lí eastwards as well.^[1]

The church (or monastery) of Cuil Raithin on the shore of the River Bann lay in Eilne and was said to have been founded by Cairbre, who subsequently became its bishop.^[9] According to the Tripartite Life of St. Patrick, written in the 9th-century, the Dál nAraidi had granted this church to Saint Patrick.^[9]

Dál nAraidi in Tuaiscirt is said to have corresponded to the later baronies of Dunluce Lower and North East Liberties of Coleraine,^[10] and appears to correspond to the trícha cét of An Tuaiscert, which became the basis for the medieval deanery and Anglo-Norman cantred of Twescard.^[3] A sub-division of in Tuaiscirt called Cuil an Tuaiscirt, meaning the "nook/corner" of Dál nAraidi in Tuaiscirt, was located in the north-west of the petty-kingdom near Coleraine. Its territory would form the basis of the later barony of North East Liberties of Coleraine.