What is the longest river in Ireland?

The longest river in Ireland is the River Shannon, at 360.5 km (224.0 miles). It is named after Sionna, a Celtic goddess. This river develops into three lakes along its course, Lough Allen, Lough Ree and Lough Derg. Of these, Lough Derg is the largest. The Shannon enters the Atlantic Ocean at the Shannon Estuary.

The Shannon divides the west of Ireland (principally the province of Connacht) from the east and south (Leinster and most of Munster). County Clare, being west of the Shannon but part of the province of Munster, is the major exception. The river represents a major physical barrier between east and west, with fewer than thirty crossing points between Limerick city in the south and the village of Dowra in the north.

Today, experts typically state that the River Shannon is closely bound up with Ireland's social, cultural, military, economic and political history.