Lough Ree, Lake in the Shannon, County Westmeath, Ireland

Lough Ree is the middle and second-largest of the three main lakes on the River Shannon, lying between counties Longford and Westmeath on the east and Roscommon on the west. Its northern part holds Inchcleraun (Inis Cloithreann), site of an early Christian monastery with remains of several ancient churches. The lake is bordered by bog and supports a small commercial eel fishery.

Viking fleets used Lough Ree as a base from the 9th century; in 845 they built a fortified stronghold on the lake. The Annals of Inisfallen record that in 988 Brian Boru put a fleet of 300 boats on Loch Rí and harried Mide. Families lived on islands such as Inchcleraun and Inchmore until the 1950s, when they were rehoused ashore.

Lough Ree's Irish name, Loch Rí, means King's Lake. The lake supports a small commercial eel fishery, and locals know the "eels on wheels" truck that carries the catch. Brendan Shine's 1973 song "Where The 3 Counties Meet" is about the lake.

Boats can be launched at Athlone harbour at the southern end of the lake, while Lanesborough lies at the northern end. The lake is a Special Area of Conservation, and invasive quagga mussels were found there in 2021, so check, clean and dry equipment. The 33.91 km length was first swum solo by Jim O'Connor in 2012.

Hodson Pillar, a monument on one of the lake's islands, was long cited as the most central point in Ireland, until Ordnance Survey Ireland recalculated the centre in 2022 and placed it near Castletown Geoghegan in County Westmeath. The lake also holds a small commercial eel fishery, known locally for its "eels on wheels" truck.