The Longest Rivers in the United Kingdom

January 10, 2024

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The Rivers Thames, one of the longest rivers in the UK

The UK isn’t just about big cities like London, Edinburgh, and Manchester. Head just a few miles out of town, and you’ll be greeted with lush green fields, tree-lined meadows, and rolling hills. This picturesque scenery is largely shaped by rivers. For centuries, they’ve been winding through the UK, changing the landscape by eroding rock and moving sediment.

But the UK’s rivers play a much more important role than simply contributing to the aesthetics of the countryside. They’re essential to the growth of the UK’s towns and cities, providing a vital source of fresh water for people, farming, and industry. And they support all kinds of plant, insect, and animal life. From willows and reeds to water voles and otters, fish, newts, and frogs to kingfishers and herons, rivers are essential for providing habitats that enable the UK’s wildlife to thrive.

Read on as we reveal the 10 longest rivers in the UK.

1. River Severn

Wide shot of the River Severn and the Severn Bridge in the distance
Severn Bridge over the River Severn
Length: 354 km (220 miles)
Country: Wales, England
Mouth: Severn Estuary

Stretching for 354 kilometers through England and Wales, the River Severn is the longest river in the UK. 

The river rises in Wales’s Cambrian Mountains and travels through the counties of Shropshire, Worcestershire, and Gloucestershire before emptying into the Severn Estuary, which discharges into the Bristol Channel. Some of the major towns and cities the River Severn passes through include Shrewsbury, Gloucester, Worcester, and Bristol, and its main tributaries are the River Vyrnwy, the River Tern, the River Teme, the River Avon, and the River Stour.

As well as being the UK’s longest river, it is the widest river in the UK, it has the fastest flow rate of any UK river, and it’s got the UK’s longest riverside walking trail.

Some of the wildlife that can be found in and around the river include carp, brown trout, eels, otters, badgers, various types of shorebirds, and the endangered five-spot ladybug.

2. River Thames

River Thames winding from Tower Bridge to the Shard
River Thames winding through London
Length: 346 km (215 miles)
Country: England
Mouth: Thames Estuary

The UK’s second-longest river is the Thames, which flows through southern England for 346 kilometers. Because it passes through London, the Thames is arguably the UK’s most famous river, and with depths of up to 66 feet, it is also the deepest.

The River Thames rises at Thames Head in the county of Gloucestershire and empties into the North Sea via the Thames Estuary near Tilbury in Essex and Gravesend in Kent. In addition to London, some of the other Towns and cities it travels through include Oxford, Abingdon, Reading, Windsor, Henley-on-Thames, and Kingston upon Thames.

Considering its length and width, the River Thames’s discharge is low. This is because it is heavily abstracted for drinking water, and it runs through some of the driest parts of Britain. Some of the river’s other notable features are its 80-plus islands, 50-plus tributaries, and walking trail, which enables people to walk almost the entire length of it.

The Thames supports an abundance of wildlife, including various types of gull, the rare black swan, eels, and — because the river contains both seawater and freshwater — more than 100 species of seawater and freshwater fish. Bottlenose dolphins, harbor porpoises, and seals have also been spotted in the Thames and the Thames Estuary.

3. River Trent

Building on the Victoria Embankment on the River Trent in Nottingham
Victoria Embankment along the River Trent
Length: 297 km (185 miles)
Country: England
Mouth: Humber Estuary

The River Trent flows from its source on the southern edge of Biddulph Moor in Staffordshire, through the towns and cities of Stoke-on-Trent, Stone, Burton upon Trent, and Nottingham before draining into the Humber Estuary and the North Sea. Located between the counties of Lincolnshire and Yorkshire, the estuary is considered by some to be the boundary between the Midlands and Northern England. 

Sadly, farming, navigation, mineral extraction, and drainage works have reduced the amount of natural habitat around the river, although nature reserves have been constructed to provide refuge for species like wildfowl, wading birds, kingfishers, otters, and American mink.

4. River Wye

River Wye and the village of Goodrich as seen from Symonds Yat Rock
River Wye and the village of Goodrich in Herefordshire
Length: 250 km (155 miles)
Country: Wales, England
Mouth: Severn Estuary

The River Wye forms much of the border between the countries of England and Wales, beginning from its source in Wales’s Cambrian Mountains and ending in the Severn Estuary.

Running through several villages and towns and just one city — Hereford — the River Wye is one of the most rural rivers on this list. Most notably, it passes through the Wye Valley — an area of Outstanding Natural Beauty.

The river’s remoteness makes it a haven for wildlife, with many species using it as a migration route and breeding ground. Some of the species the River Wye supports include dolphins, harbor porpoises, seals, otters, minks, water voles, kingfishers, salmon, and eels.

5. River Great Ouse

Buildings in St Ives reflected in the calm waters of the River Great Ouse
A summer’s day on the River Great Ouse, St Ives
Image credit: Chris Boland
Length: 230 km (143 miles)
Country: England
Mouth: The Wash

From its source in Syresham in Northamptonshire, the River Great Ouse flows mostly north and east, passing through the counties of Buckinghamshire, Bedfordshire, Cambridgeshire, and Norfolk before emptying into The Wash near King’s Lynn in Norfolk. Along its journey, the river takes in several cities, including Milton Keynes, Bedford, and Ely, as well as smaller towns like St Ives and Godmanchester.

Had the river not been extensively modified to deal with flooding and provide a better route for barges, its course would have regularly changed after heavy rainfall.

Although pollution is a problem — as it is with all of the rivers on this list — water quality is improving, and otters have returned to the River Great Ouse in such large numbers that fences have been erected to protect fish stocks. Seals have also been spotted in the river as far upstream as Bedford.

6. River Ure-River Ouse

A summer's day on the River Ouse in York
River Ouse, York
Length: 208 km (129 miles)
Country: England
Mouth: Humber Estuary

The river begins as the River Ure in the North Yorkshire Moors, flows south for 119 kilometers, and then becomes the River Ouse, which flows for another 89 kilometers before draining into the Humber Estuary. Combined, the rivers pass through the towns and cities of Hawes, Ripon, Boroughbridge, York, Selby, and Goole.

The River Ouse is fed by many tributaries, such as the River Derwent, River Aire, River Wharfe, River Swale, and River Foss, but the River Ure is the largest. The Ure’s tributaries include the River Swale and the River Skell.

The Ouse Valley, in the River Ouse’s drainage basin, is home to large populations of badgers, rabbits, roe deer, and red foxes, and birds like golden plovers, curlews, and oystercatchers can also be seen in the area. Fish species such as brown trout, chub, grayling, perch, and roach live in the river system itself.

7. River Tay

Drone view of the River Tay and the city of Perth on a beautiful summer's day
River Tay and the city of Perth
Length: 188 km (117 miles)
Country: Scotland
Mouth: Firth of Tay

The first Scottish river to feature on this list, the River Tay flows east from its source on the slopes of Ben Lui in western Scotland to the Firth of Tay, just south of Dundee. Along the way, it flows across the Scottish Highlands and through Loch Dochart, Loch Iubhair, Loch Tay, Strathtay, and Perth, where it becomes tidal.

By discharge, the River Tay is the UK’s largest river, and it is capable of holding more water than both the River Severn and the River Thames combined.

A Site of Special Scientific Interest and a Special Area of Conservation, the River Tay has a high level of biodiversity, and it is particularly noted for its salmon, otter, brook lamprey, river lamprey, and sea lamprey species. As one of the best salmon rivers in Western Europe, it attracts fishermen from all over the world.

8. River Clyde

Dawn at Finlaystone foreshores on the bank of the River Clyde
The sun rising over the River Clyde
Length: 176 km (109 miles)
Country: Scotland
Mouth: Firth of Clyde

Another river flowing entirely through Scotland, the River Clyde begins where the Daer Water and Potrail Water streams meet near the town of Elvanfoot in southern Scotland. It then makes its way generally northeastward through Lanark, Wishaw, Larkhall, Blantyre, Glasgow, Renfrew, Dumbarton, and Port Glasgow before draining into the Firth of Clyde.

Like all of the rivers on this list, the Clyde supports an array of wildlife both in and around its waters. As well as being home to marine mammals like seals, harbor porpoises, and otters, at least 17 species of seabirds, including gannets, guillemots, and cormorants, live in the river’s surrounding areas. A top fishing spot, species that live in the river include cod, pollock, and basking sharks — although basking sharks are a protected species in Scotland and cannot be fished.

9. River Spey

The New Spey Bridge at Grantown spanning the River Spey
The New Spey Bridge spanning the River Spey in Scotland
Length: 172 km (107 miles)
Country: Scotland
Mouth: Moray Firth

Emerging from Loch Spey in the Highlands, the River Spey flows northeast to drain into the Moray Firth at Spey Bay. Its course takes in multiple towns and villages, such as Newtonmore, Aviemore, Grantown-on-Spey, and Aberlour. 

While the River Spey is only the third-longest river in Scotland, it is the country’s fastest-flowing, which makes it a popular canoeing destination.

The river’s large quantities of Atlantic Salmon also make it a popular fishing spot. Other species that can be found in the River Spey’s waters include the Eurasian Otter, Grey Seal, and Bottlenose Dolphin.

10. River Nene

Mist over the River Nene at Woodford Lock in Northamptonshire
River Nene at Woodford Lock, Northamptonshire
Length: 161 km (100 miles)
Country: England
Mouth: The Wash

The final river to feature on this list is the River Nene, with a length of 161 kilometers.

This English river rises from three sources in the county of Northamptonshire and meanders in an easterly direction through the towns and cities of Earl’s Barton, Wellingborough, Thrapston, Oundle, Peterborough, March, Wisbech, Sutton Bridge, and Gedney Drove End, before finally emptying into The Wash.

Historically, the river played a key role in the Industrial Revolution and was home to Marvell’s Mill — England’s first water-powered cotton spinning mill. Today, the river — which is navigable for 142 kilometers — is used mainly for recreation.

The River Nene supports plenty of wildlife, from herons and kingfishers to otters. A protected area near The Wash provides a sanctuary for many rare and migrating birds, and it even attracts birds of prey.

Overview: The UK’s longest rivers

RankRiverCountryLength (km)Length (miles)
1River SevernWales, England354220
2River ThamesEngland346215
3River TrentEngland297185
4River WyeWales, England250155
5River Great OuseEngland230143
6River Ure-River OuseEngland208129
7River TayScotland188117
8River ClydeScotland176109
9River SpeyScotland172107
10River NeneEngland161100
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