The River Shannon (Irish: Abhainn na Sionainne, an tSionainn, an tSionna), at 360.5 km (224 miles) in length, is the longest river in the British Isles. It drains the Shannon River Basin, which has an area of 16,865 km2 (6,512 sq mi), – approximately one fifth of the area of the island of Ireland. The river takes its name after Sionna, a Celtic goddess.