Bann longest river of Northern Ireland, rising as the Upper Bann in the Mourne Mts. and flowing 40 mi (64 km) NW to the southern end of Lough Neagh.

The longest river in Ireland is the River Shannon, 386 km (240 mi). The river develops into three lakes along the way to the Atlantic ocean, Lough Allen, Lough Ree and Lough Derg. Of the three, Lough Derg is the largest. The Shannon enters the Atlantic Ocean at the Shannon Estuary. Other big rivers include the River Liffey, River Lee, River Swilly, River Blackwater, River Nore, River Suir, River Barrow, River Bann and River Boyne. The Lee, Blackwater, and Barlow rivers are all rivers on the eastern side of Ireland. There are over a hundred fifty rivers in Ireland.
Ireland's River Liffey is the main river in Dublin.It begins at Sally Gap near Kippure in County Wicklow, just south of Dublin. It travels about 78 miles through the center of Dublin and out into Dublin Bay, eventually it reaches the Irish Sea.