A by-election was held in the Dáil constituency of Donegal in Ireland on Thursday, 6 November 1980. It followed the death of the Ceann Comhairle Joseph Brennan on 13 July 1980.
A government motion to issue the writ of election to fill the vacancy was agreed by the Dáil on 16 October 1980. The by-election was won by Fianna Fáil candidate Clement Coughlan.
Coughlan died in a road accident in early 1983, leading to the 1983 Donegal South-West by-election.