Donegal, town (1991 pop. 2,193), Co. Donegal, NW Republic of Ireland, on the River Eske at the head of Donegal Bay. The town is a seaport with wool mills. Its castle, stronghold of the O'Donnells, was rebuilt in 1610. There are ruins of a Franciscan monastery, founded in 1474, where the Annals of the Four Masters, a history of the world, was compiled between 1632 and 1636.