Longest Riviers of the United Kingdom
| Name of watercourse | Length | Remotest source | Mouth |
| Severn (for 254 km) | 354 km (220 mi) | Lake on E. side of Plinlimmon, Powys | Bristol Channel |
| Thames (for 178 km) Isis (69 km) - Churn | 346 km (215 mi) | Seven Springs, Glos | North Sea |
| Trent (for 236 km) - Humber (61 km) | 297 km (185 mi) | Biddulph Moor, Staffs | North Sea (Humber) |
|
Aire (for 126 km) - (Yorkshire) Ouse (72 km) - Humber (61 km) |
259 km (161 mi) | NW of North Yorkshire | North Sea (Humber) |
|
Ouse (Great or Bedford) |
230 km (143 mi) | Nr Brackley, Northants | The Wash |
| Wye (or Gwy) | 215 km (135 mi) | Plinlimmon, Powys | Into Severn S of Chepstow |
| Tay (for 150 km) - Tummel | 188 km (117 mi) | (Tay) Beinn Oss (Perthshire and Kinross) | North Sea |
| Nene | 161 km (100 mi) | Nr Naseby, Northants | The Wash |
|
Clyde (inc. Daer Water) |
158 km (98 mi) | Nr Earncraig Hill, South Lanarkshire | Firth of Clyde (measured to Port Glasgow) |
| Spey | 158 km (98 mi) | Loch Spey, Highland | North Sea |
| Tweed | 155 km (97 mi) | Tweed's Well, Borders | North Sea |
| Dee (Aberdeenshire) | 137 km (85 mi) | W of Cairn Toul, Aberdeenshire | North Sea |
| Avon (Warwickshire) | 137 km (85 mi) | Nr Naseby, Northants | Into Severn at Tewkesbury |
| Don (Aberdeenshire) | 130 km (81 mi) | Carn Cuilchathaidh, Aberdeenshire | North Sea |
| Tees | 127 km (79 Mi) | Cross Fell, Cumbria | North Sea |
|
Bann (Upper Bann - Lough Neagh - Lower Bann) |
122 km (76 mi) | Mountains of Mourne | Atlantic Ocean |
| Tyne (for 55 km) - North Tyne (63 km) | 119 km (73 mi) | Cheviots, between Peel Fell and Carter Fell Northumberland | North Sea |
| Dee (Cheshire) | 113 km (70 mi) | Bala Lake, Caerarfonshire & Merioneth | Irish Sea |
| Eden | 111 km (69 mi) | Pennines, SE of Kirkby Stephen, Cumbria | Solway Firth, Irish Sea |
| Usk | 105 km (65 mi) | Talsarn Mt, Powys | Bristol Channel |
| Wear | 105 km (65 mi) | W of Wearhead, Northumberland | North Sea |
Lochs and Lakes in Northern Ireland
| Name |
Area (sq. km) |
Area (sq. mi) |
Max. length | Max. breadth | Max. depth |
| Lower Neagh | 381.7 | 147.4 |
28 km 18 mi |
17 km 11 mi |
31m 102 ft |
| Lower Lough Erne | 105 | 40.6 |
28 km 18 mi |
8.8 km 5.5 mi |
68m 226 ft |
Lochs and Lakes in Scotland
| Name |
Area (sq. km) |
Area (sq. mi) |
Max. length | Max. breadth | Max. depth |
| Loch Lomond | 71.2 | 27.5 |
36.4 km 22.6 mi |
8 km 5 mi |
189m 623 ft |
| Loch Ness | 56.6 | 21.9 |
36.6 km 22.8 mi |
3.2 km 2 mi |
228m 751 ft |
| Loch Awe | 38.7 | 15.0 |
41 km 25.5 mi |
3.2 km 2 mi |
93m 307 ft |
| Loch Maree | 28.4 | 11.0 |
21.7km 13.5 mi |
3.2 km 2 mi |
111m 367 ft |
| Loch Morar | 26.6 | 10.3 |
18.5km 11.5 mi |
2.4 km 1.5 mi |
309m 1017 ft |
| Loch Tay | 26.3 | 10.2 |
23.4 km 14.6 mi |
1.7 km 1.1 mi |
154m 508 ft |
Lochs and Lakes in England
| Name |
Area (sq. km) |
Area (sq. mi) |
Max. length | Max. breadth | Max. depth |
| Windermere | 14.7 | 5.7 |
16.8 km 10.5 mi |
1.5 km 0.9 mi |
66m 219 ft |
| Ullswate | 8.9 | 3.4 |
11.8 km 7.4 mi |
1.0 km 0.9 mi |
62m 219 ft |
| Bassenthwaite Water | 5.3 | 2.1 |
6.1 km 3.8 mi |
1.2 km 0.7 mi |
21m 70 ft |
| Derwentwater | 5.3 | 2.1 |
4.6 km 2.9mi |
1.9 km 1.2 mi |
21m 72 ft |
Lochs and Lakes in Wales
| Name |
Area (sq. km) |
Area (sq. mi) |
Max. length | Max. breadth | Max. depth |
| Lake Vrywy (dammed) | 8.2 | 3.2 |
7.5 km 4.7 mi |
0.6 km 0.3 mi |
36 m 120 ft |
| Bala Lake (Llyn Tegid) | 4.3 | 1.7 |
6.1 km 3.8 mi |
0.5 km 0.3 mi |
38m 125 ft |