The River Shannon is the major river on the island of Ireland, and at 360 km in length, is the longest river in the British Isles. It drains the Shannon River Basin, which has an area of 16,900 km2 (6,525 sq mi), – approximately one fifth of the area of Ireland.

Shown here are all the major rivers and tributaries of Ireland with their lengths. Starting with the Northern Ireland rivers, and going in a clockwise direction, the rivers are listed in regard to their entry into the different seas: the Irish Sea, the Celtic Sea and the Atlantic Ocean. Also shown are two tables. Table 1 shows the longest rivers in Ireland with their lengths, the counties they flow through, and their catchment areas. Table 2 shows the largest rivers in Ireland in cubic metres per second.