County Donegal is a county of Ireland in the province of Ulster and in the Northern and Western Region. It is named after the town of Donegal in the south of the county. It has also been known as County Tyrconnell or Tirconaill, after the historic territory. Donegal County Council is the local council and Lifford is the county town.

There are four provinces of Ireland: Connacht, Leinster, Munster and Ulster. The Irish word for this territorial division, cúige, meaning "fifth part", suggests that there were once five, and at times Meath has been considered to be the fifth province. In the medieval period, however, there were often more than five. The number of provinces and their delimitation fluctuated until 1610, when they were permanently set by the English administration of James I. The provinces of Ireland no longer serve administrative or political purposes but function as historical and cultural entities.