South Donegal was a UK Parliament constituency in Ireland, returning one Member of Parliament 1885–1922.
Prior to the 1885 general election the area was part of the Donegal constituency.
From 1922, on the establishment of the Irish Free State, it was not represented in the UK Parliament.
This constituency comprised the southern part of County Donegal, consisting of the baronies of Banagh and Tirhugh.
This article about a Historic Westminster constituency in Ireland is a stub.