The Donegal constituency was created in 1921 under the Government of Ireland Act 1920, for the 1921 election to the House of Commons of Southern Ireland, whose members formed the 2nd Dáil. It elected 6 deputies in 1921, and again at the 1922 general election. It covered the whole territory of County Donegal in north-west Ireland. Under the Electoral Act 1923, the constituency's boundaries remained unchanged, and were defined simply as "the administrative county of Donegal". However, its representation was increased from 6 to 8 seats. The Donegal constituency was abolished by the Electoral Act 1935, with effect from the 1937 general election. It was replaced by two new constituencies: the 4 seat Donegal East and the 3 seat Donegal West.
1977 to 1981
A Donegal constituency was re-established under the Electoral Act 1974, and first used at the 1977 general election to the 21st Dáil. The new 5 seat constituency did not cover all of County Donegal; an area in the south of the county, including the rural hinterland of Ballyshannon and the town of Bundoran, was included in the Sligo–Leitrim constituency. The revived constituency was short-lived, as under the Electoral Act 1980, it was replaced by two new 3 seat constituencies, Donegal North-East and Donegal South-West.
Since 2016
In 2012 the Constituency Commission proposed that at the next general election a new constituency called Donegal be created. The report proposed changes to the constituencies of Ireland so as to reduce the total number of TDs from 166 to 158. It was established by the Electoral Act 2013. It replaced the constituencies of Donegal North-East and Donegal South-West and comprises the county of Donegal except for the area south of Donegal town around Ballyshannon and Bundoran, which is in the Sligo–Leitrim constituency. The 2013 Act defines the constituency as:
A by-election was held on 20 November 1924 to fill the vacancy caused by the resignation on 1 August 1924 of the Cumann na nGaedheal TD Peter Ward. There were only two candidates, and the winner was the Cumann na nGaedheal candidate Denis McCullough.
The 1923 general election to the 4th Dáil was the first in the Donegal constituency where the number of candidates exceeded the number of seats. Under the Electoral Act 1923, Donegal's representation had been increased from six to eight seats, and these were contested by no less than 19 candidates.
1922 general election
As at the 1921 general election, Sinn Féin stood one candidate for every seat, except those for two Dublin constituencies; the treaty had divided the party between 65 pro-treaty candidates, 57 anti-treaty and 1 nominally on both sides. Unlike the elections a year earlier, other parties stood in most constituencies forcing single transferable vote elections, with Sinn Féin losing 30 seats. In Donegal, Sinn Féin's six outgoing TDs from the 2nd Dáil were elected unopposed, Socialist Republican, Jack White having withdrawn his candidacy. Two had opposed the treaty, and four supported it; they are listed here in alphabetical order
1921 general election
At the 1921 general election to the 2nd Dáil, no seats were contested in the 26 counties which became the Irish Free State. In Donegal, six Sinn Féin candidates were nominated for the constituency's eight seats. Major Robert L Moore, who had contested East Donegal in 1918, was selected as the Unionist candidate by 22 April 1921 but was described on 15 May 1921 as 'having at the last moment withdrawn'. No ballot was needed, and all six candidates were elected unopposed after the close of nominations on 24 May 1921. The 6 TDs elected are listed here in alphabetical order:
