It is named after the town of Donegal (Dún na nGall) in the south of the county. Donegal County Council is the local council for the county and Lifford serves as the county town. The population of the county was 161,137 according to the 2011 census. It has also been known as (County) Tyrconnell (Tír Chonaill), after the historic territory of the same name.
The county is the most mountainous in Ulster consisting chiefly of two ranges of low mountains; the Derryveagh Mountains in the north and the Bluestack Mountains in the south, with Mount Errigal at 749 metres (2,457 ft) the highest peak. It has a deeply indented coastline forming natural sea loughs, of which both Lough Swilly and Lough Foyle are the most notable. The Slieve League cliffs are the sixth-highest sea cliffs in Europe, while Malin Head is the most northerly point on the island of Ireland.