This article is about the medieval Irish kingdom. For the royal fort of that kingdom, see Grianan of Aileach
Ailech (modern Irish Aileach or Oileach) was a medieval kingdom (450 - 1617 AD) in Ireland, roughly centred on modern-day County Donegal and the Inishowen peninsula in Ulster.
The Kings of Ailech belonged to the northern Uí Néill and took their name from the Grianán of Ailech (Irish: Grianán Ailigh), a hillfort on top of Greenan Mountain in modern County Donegal. The restored fort stands in a commanding position at the base of the Inishowen peninsula overlooking Lough Swilly to the west and Lough Foyle to the east.
- "Cenel nEogain Kings of Ailech 700-1185", pages 194-195 in A New History of Ireland, volume IX, ed. Byrne, Martin, Moody, 1984.
- T. M. Charles-Edwards, Early Christian Ireland
- Francis J. Byrne, Irish Kings and High-Kings