Ailech was a medieval kingdom in Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, roughly centred on modern-day County Tyrone

County Tyrone

Historically Tyrone stretched as far north as Lough Foyle, and comprised part of modern day County Londonderry east of the River Foyle. The majority of County Londonderry was carved out of Tyrone between 1610-1620 when that land went to the Guilds of London to set up profit making schemes based on...

 and the Inishowen

Inishowen

Inishowen is a peninsula in County Donegal, part of the Province of Ulster in the north of Ireland. It is also the largest peninsula in all of Ireland. Inishowen is a picturesque location with a rich history...

 peninsula in Ulster

Ulster

Ulster is one of the four provinces of Ireland, located in the north of the island. In ancient Ireland, it was one of the fifths ruled by a "king of over-kings" . Following the Norman invasion of Ireland, the ancient kingdoms were shired into a number of counties for administrative and judicial...

.

The Kings of Ailech

Kings of Ailech

The Kings of Ailech belonged to the northern Uí Néill and took their name from the Grianán of Ailech , a hillfort on top of Greenan Mountain in modern County Donegal...

 belonged to the northern Uí Néill

Uí Néill

The Uí Néill are Irish and Scottish dynasties who claim descent from Niall Noigiallach , an historical King of Tara who died about 405....

 and took their name from the Grianán of Ailech

Grianan of Aileach

The Grianán of Aileach is a group of historic monuments in County Donegal, Ireland built on the hill of Grianán which is 244 metres high. Most writers have identified the site as being the great “royal fort” of Aileach...

 , a hillfort on top of Greenan Mountain in modern County Donegal

County Donegal

County Donegal is a county in Ireland. It is part of the Border Region and is also located in the province of Ulster. It is named after the town of Donegal. Donegal County Council is the local authority for the county...

. The restored fort stands in a commanding position at the base of the Inishowen peninsula overlooking Lough Swilly

Lough Swilly

Lough Swilly in Ireland is a glacial fjord or sea inlet lying between the western side of the Inishowen Peninsula and the Fanad Peninsula, in County Donegal. Along with Carlingford Lough and Killary Harbour it is one of three known glacial fjords in Ireland....

 to the west and Lough Foyle

Lough Foyle

Lough Foyle, sometimes Loch Foyle , is the estuary of the River Foyle in Ulster. It starts where the Foyle leaves Derry. It separates the Inishowen Peninsula in County Donegal, Republic of Ireland from County Londonderry in Northern Ireland.-Transport:...

to the east.