Longest rivers of the United Kingdom

The Severn Bridges crossing near the mouth of the River Severn.

The River Thames in London.

The River Tay in Perth, by measured flow the largest in Great Britain.

This is a list of the longest rivers of the United Kingdom.

Longest rivers of the United Kingdom

Rank	River	Length (miles)	Length (km)	Mean Flow (m3/s)	Country
1	River Severn	220	354	107.4	Wales/England
2	River Thames	215	346	65.4	England
3	River Trent	185	297	89.0	England
4	River Great Ouse	143	230	15.6	England
5	River Wye	134	215	73.1	Wales/England
6	River Ure/River Ouse, Yorkshire	129	208	69.8	England
7	River Tay	117	188	179.0	Scotland
8	River Clyde	109	176	48.5	Scotland
9	River Spey	107	172	65.7	Scotland
10	River Nene	100	161	9.3	England
11	River Bann / Lough Neagh	99	159	92.2	Northern Ireland
12	River Tweed	96	155	81.7	Scotland/England
13	River Avon, Warwickshire	96	154	17.3	England
14	River Eden, Cumbria	90	145	53.7	England
15	River Dee, Aberdeenshire	87	140	47.8	Scotland
16	River Witham	82	132	5.2	England
17	River Teme	81	130	18.2	Wales/England
18	River Don, Aberdeenshire	80	129	21.3	Scotland
18	River Foyle	80	129	58.8	Northern Ireland/Republic of Ireland
20	River Teifi	75	122	29.5	Wales
20	River Tywi	75	121	39.9	Wales
20	River Ribble	75	120	34.0	England
20	River Avon, Bristol	75	120	22.2	England
24	River Tyne	73	118	45.2	England
25	River Derwent, Yorkshire	72	115	17.4	England
26	River Aire	71	114	36.5	England
26	River Nith	71	114	36.5	Scotland
28	River Tees	70	113	22.2	England
28	River Medway	70	113	11.7	England
28	River Mersey	70	113	37.1	England
31	River Dee, Wales	70	112	34.1	Wales/England
31	River Don, South Yorkshire	70	112	16.3	England

There seems to be little consensus in published sources as to the lengths of rivers, nor much agreement as to what constitutes a river. Thus the River Ure and River Ouse can be counted as one river system or as two rivers. If it is counted as one, the River Aire/ River Ouse/Humber system would come fourth in the list, with a combined length of 161 miles (259 km); and the River Trent/Humber system would top the list with their combined length of 222 miles (357 km). Also, the Thames tributary, the River Churn, sourced at Seven Springs, adds 14 miles (23 km) to the length of the Thames (from its traditional source at Thames Head). The Churn/Thames' length at 229 miles (369 km) is therefore greater than the Severn's length of 220 miles (354 km). Thus, the combined Churn/Thames river would top the list. Sue Owen et al., in their book on rivers, generally restrict the length to the parts that bear the same name. Thus the River Nene is quoted at 100 miles (160 km), but would be around 5 miles (8 km) more if the variously named sources were included. Many of the above lengths are considerably different from Sue Owen's list, some longer and some shorter.

Where a river ends in an estuary the conventional British approach has been to treat the river as ending at the end of the administrative zone. Thus the Severn ends at the mouth of the Bristol Avon and the Thames at the Yantlet Line. The currently accepted end of the Severn Estuary is about 18.5 miles (29.8 km) further, and the Port of London's authority stretches now to Margate, 30 miles (48 km) further. Other countries have different conventions, making comparisons of limited value.

See also

• List of rivers of England
• List of rivers of Ireland
• List of rivers of Scotland
• List of rivers of Wales
• List of rivers in the Isle of Man
• Terminology
  • Estuary
  • Firth
  • Floodplain
  • River
  • River delta
  • Source (river or stream)
  • Tributary
  • Canal & River Trust
  • Canals of the United Kingdom
  • Geography of the United Kingdom
  • List of lakes in the United Kingdom
  • Reservoirs and dams in the United Kingdom
  • Waterfalls of the United Kingdom
  • Waterways in the United Kingdom