Donegal, a maritime county of Ireland, bounded N. and W. by the Atlantic, E. by the counties of Londonderry, Tyrone, and Fermanagh, and S. by the counties of Fermanagh and Leitrim, and by Donegal bay; area, 1,805 sq. m.; pop. in 1871, 217,992. The shores are deeply indented by bays, the most important of which, Lough Swilly, penetrates 25 m. into the land. There are numerous islands off the coast, and several lakes within the county. The general aspect of the surface is mountainous. Nearly two thirds of the land consist of bogs or sterile hills, incapable of cultivation. The chief rivers are the Swilly and the Finn, and the principal towns Ballyshannon, Let-terkenny, Ramelton, Donegal, and Killybegs. Oats, barley, flax, and potatoes are the staple agricultural productions. In 1868 there were 231,245 acres under cultivation. The fishery districts in 1867 employed 1,074 boats, with 8,700 men and 778 boys. Linen manufacture is carried on, and there are also many flour mills; the export trade is chiefly through the port of Londonderry. Capital, Lifford. - The town of Donegal (pop. about 1,000), at the head of a bay of the same name, 29 m.

N. E. of Sligo, gives the titles of marquis and earl to the Chichester family.