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, 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.