Portrunny Harbour is situated on the shores of Lough Ree along the River Shannon. The River Shannon is 259km in length, originates in the Cuilcagh Mountains in County Cavan and enters the Atlantic Ocean just below Limerick City.

Lough Ree ‘Lake of the Kings’ is the second largest lake on the River Shannon.  The lake is almost 30km from Lanesborough in Co Longford to Athlone in Co Westmeath.  Lough Ree is notable for numerous interesting islands, including  Inchcleraun (Quaker Island).