County Donegal is a county in Ireland. It is part of the Border Region and is in the province of Ulster. It is named after the town of Donegal (Dún na nGall) in the south of the county.
In terms of size and area, it is the largest county in Ulster and the fourth-largest county in all of Ireland. Uniquely, County Donegal shares a small border with only one other county in the Republic of Ireland – County Leitrim. The greater part of its land border is shared with three counties of Northern Ireland: County Londonderry, County Tyrone and County Fermanagh. While Lifford is the county town, Letterkenny is by far the largest town in the county. According to the 1841 Census, County Donegal had a population of 296,000 people. As a result of famine and emigration, the population had reduced by 41,000 by 1851 and further reduced by 18,000 by 1861.