Longest Rivers in England, Wales, Scotland, and Northern Ireland

River lengths vary by source definition; here are consensus rankings:

England

1. River Severn – 220 mi (354 km) (also Wales)
2. River Thames – 215 mi (346 km)
3. River Trent – 185 mi (298 km)
4. River Great Ouse – 143 mi (230 km)
5. River Wye – 134 mi (215 km) (also Wales)

Wales

1. River Severn – 220 mi
2. River Wye – 134 mi
3. River Usk – 103 mi (166 km)
4. River Dee – 98 mi (158 km) (also England)
5. River Teifi – 75 mi (121 km)

Scotland

1. River Tay – 117 mi (188 km)
2. River Spey – 107 mi (172 km)
3. River Clyde – 106 mi (170 km)
4. River Tweed – 97 mi (156 km) (also England)
5. River Forth – 68 mi (109 km)

Northern Ireland

1. River Bann – 92 mi (148 km) (incl. Lough Neagh)
2. River Foyle – 80 mi (129 km) (border with ROI)
3. River Erne – 72 mi (116 km) (mostly ROI)
4. River Lagan – 45 mi (72 km)
5. River Blackwater – 40 mi (64 km)

Notes: Severn is UK's longest; Tay is Scotland's longest by flow; Bann is NI's longest. Many rivers cross borders—governance involves multiple agencies.