The Longest Rivers in Northern Ireland

It’s home to the UK’s biggest lake, but what about rivers? Read on to learn about the longest rivers in Northern Ireland.

Travel and Exploration
20 March 2023

Making up approximately a sixth of the island of Ireland, Northern Ireland’s gentle landscape covers approximately 5,236 square miles. What’s more, water is at the core of its geography, with Loch Neagh acting as a central basin around which its highlands rise. There are also around 450 rivers in Northern Ireland, each one supporting a range of flora and fauna.

In this article, we’ll explore Northern Ireland’s longest rivers, starting with the biggest river in Northern Ireland, the Bann.

River Bann: The Biggest River in Northern Ireland

The River Bann (Photo: Leonid Andronov via Getty Images)

Length: 80 miles

Travelling through the counties of Down, Armagh, Antrim and Derry, the Bann is the largest river in Northern Ireland. The length of its journey from the southeastern Mourne Mountains to the northwest coast, where it empties into the Atlantic, is usually cited as 80 miles. This increases to 99 miles or so if its run through Lough Neagh – the biggest lake in the UK – is taken into account. Nevertheless, it’s traditionally split into the Upper and Lower Bann, divided by this lake at roughly halfway.

The basin of the Bann, an area of some 2,230 square miles, is home to a variety of wildlife, with at least two of its wetlands registered as Sites of Scientific Interest. Wildfowl and otters are just two examples of its residents. Meanwhile, Atlantic salmon, brown trout, and eel are among the aquatic life in the river.

River Erne

River Erne (Photo: MediaProduction via Getty Images)

Length: 64 miles

Beginning and ending in the Republic of Ireland, it’s the middle section of the River Erne that makes it one of the longest rivers in Northern Ireland. Popular among fishermen for its spring salmon, sea trout and char, it counts a number of fisheries on its banks.

River Blackwater

River Blackwater (Photo: Michael Roberts via Getty Images)

Length: 50-57 miles

Known in Irish as An Abhainn Mhór, the River Blackwater runs for between 50 and 57 miles before emptying into Lough Neagh. As well as being one of Northern Ireland’s longest rivers it is also one of its most meandering. Northern Ireland’s River Blackwater should not be confused with the river by the same name in the Republic of Ireland.

River Lagan

River Lagan (Photo: Walter Bibikow via Getty Images)

Length: 45- 53 miles

The River Lagan or “Abhainn an Lagáin” rises at the mountain of Slieve Croob in County Down and travels up to 53 miles to its mouth at Belfast Lough. From there it empties into the Irish Sea. The river’s 235-square-mile basin is split between a generally agricultural character in its upper half and a more urban one in the lower stretch. In particular, it passes through the city of Belfast. Along its route, it forms the boundary between the counties of Antrim and Down.

River Roe

River Roe (Photo: via Getty Images)

Length: 34 miles

Located solely in County Londonderry, the River Roe is one of the longest rivers of Northern Ireland and one of the most environmentally significant rivers in the British Isles. In particular, it’s home to around eight percent of Northern Ireland’s spawning population of Atlantic Salmon and a considerable proportion of migratory sea trout. These factors, along with its wealth of animal and plant life, contributed towards the Roe’s basin being declared a Site of Scientific Significance and protected as such.

Longest Rivers of Northern Ireland

A tranquil river (Photo: Dani Serrano via Getty Images)

While it may be small, Northern Ireland’s longest rivers help to make it a haven for wildlife, whether in the water, on land or in the sky.


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