Rinn Lough (Irish: Claonloch, also Irish: Loch na Reanna),[1] also known as Lough Rynn, is a freshwater lake in the northwest of Ireland. It is located in south County Leitrim.
Rinn Lough measures about 4 km (2.5 mi) long and 1 km (0.6 mi) wide. It is located about 4 km (2 mi) south of Mohill. Lough Rynn Castle, a medieval castle now a hotel, occupies an estate on the lake's northeastern shore.[2]
Two smaller neighbouring lakes drain into Rinn Lough: Clooncoc Lough and Lough Errew. Rinn Lough drains south into the Rinn River flowing into Lough Forbes. Part of the river forms the Rinn River Natural Heritage Area.[2][4]
The water quality was reported to be satisfactory c. 2001 – c. 2006 maintaining a mesotrophic rating.[5][6][n 1] but given a "bad ecological status" c. 2007 – c. 2009 due to pollution.[8] Zebra mussel infestation is present.[6] The ecology of Rinn Lough, and Irish waterways, remains threatened by curly waterweed, zebra mussel, and freshwater clam invasive species.[9][10]