Roscommon–South Leitrim was a parliamentary constituency represented in Dáil Éireann, the lower house of the Irish parliament or Oireachtas, from 2007 to 2016.

The constituency elected 3 deputies (Teachtaí Dála, commonly known as TDs).

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

[2] This territory was previously represented through the constituencies of Longford–Roscommon and Sligo–Leitrim, both of which were abolished in 2007.

The Electoral (Amendment) Act 2009 defined the constituency as: and, in the county of Leitrim, the electoral divisions of: Ballinamore, Cloverhill, Corralla, Drumreilly North, Drumreilly South, Garradice, Greaghglass, Killygar, Newtowngore, Oughteragh, in the former Rural District of Ballinamore; Annaduff, Carrick-on-Shannon, Drumsna, Gortnagullion, Gowel, in the former Rural District of Carrick-on-Shannon No.