South Fermanagh was a parliament constituency in Ireland which returned one Member of Parliament to the House of Commons of the United Kingdom on the electoral system of first past the post from 1885 to 1922.

The constituency was a nationalist inclined one, but with a significant unionist minority. The Irish Parliamentary Party held the seat from 1885 to 1918.

At the 1918 general election, Sinn Féin had a limited electoral pact in Ulster with the Nationalists to avoid splitting the vote in seats Unionists might win. In South Monaghan, Sinn Féin benefited from the pact, as nationalists were advised to vote for Seán O'Mahony rather than their own candidate (the incumbent MP).^[1] O'Mahony was a prisoner interned in Lincoln Jail at the time of the election. He was the only Sinn Féin candidate elected in the six counties that became Northern Ireland who was not also returned for a seat in the rest of Ireland. After his release in 1919, he served in the Dáil Éireann.

From 1801 to 1885, County Fermanagh returned two MPs to the House of Commons of the United Kingdom sitting at the Palace of Westminster, with separate representation for the parliamentary borough of Enniskillen. Under the Redistribution of Seats Act 1885, the parliamentary county was divided into the divisions of North Fermanagh and South Fermanagh. Enniskillen ceased to exist as a parliamentary borough.^[2]

South Fermanagh was defined as:^[3]

In County Fermanagh, the baronies of Clanawley, Clankelly, Coole, Knockninny, and Magherastephana.

It was not affected by the Redistribution of Seats (Ireland) Act 1918.^[4] At the 1918 general election, Sinn Féin contested on an election manifesto with an abstentionist pledge that instead of taking its seats at Westminster, it would establish an assembly in Dublin. All MPs elected to Irish seats were invited to participate in the First Dáil convened in January 1919, but no members outside of Sinn Féin did so.^[5]

The Government of Ireland Act 1920 established the Parliament of Northern Ireland, which came into operation in 1921. The representation of Northern Ireland at Westminster was reduced from 30 MPs to 13 MPs, taking effect at the 1922 United Kingdom general election. At Westminster, North Fermanagh, South Fermanagh, North-East Tyrone, North-West Tyrone and South Tyrone were combined to form the two-seat county constituency of Fermanagh and Tyrone.^[6] An eight-seat constituency of Fermanagh and Tyrone was created for the House of Commons of Northern Ireland, which formed the basis in republican theory for representation in the Second Dáil.^[7][8]

• Walker, Brian M., ed. (1978). Parliamentary Election Results in Ireland, 1801–1922. Dublin: Royal Irish Academy. ISBN 0901714127.
• Debrett's Guide to the House of Commons and Judicial Bench. 1918. p. 220.
• Stenton, M.; Lees, S., eds. (1978). Who's Who of British members of parliament: Volume II 1886–1918. The Harvester Press.
• Leigh Rayment's Historical List of MPs – Constituencies beginning with "F"