Donegal South-West was a parliamentary constituency represented in Dáil Éireann, the lower house of the Irish parliament or Oireachtas, from 1961 to 1969 and from 1981 to 2016.

The method of election was proportional representation by means of the single transferable vote (PR-STV).

[17] On 2 July 2009, Caoimhghín Ó Caoláin (SF) proposed that the writ of election be issued to fill the vacancy.

[19] On 12 July 2010, Pearse Doherty, a Sinn Féin senator, was granted leave to bring judicial review against the government seeking a declaration that due to the length of the vacancy in Donegal South-West, the government was under a duty not to oppose a motion for a writ.

[20] On 3 November 2010, Nicholas Kearns, president of the High Court, made a declaration that there has been an unreasonable delay in moving the writ for the by-election in Donegal South-West.

The seat was won by the Fianna Fáil candidate Cathal Coughlan, brother of the deceased TD.