Which river is the longest in Great Britain?

The River Severn is the longest river in Great Britain.

The Severn rises on the Plynlimon massif in mid-Wales and runs for about 220 miles (354 kilometres). It flows through Wales and England, passing near Shrewsbury, Worcester and Gloucester before entering the Severn Estuary and Bristol Channel.

A common mix-up is the River Thames. The Thames is the longest river entirely within England, but it is shorter than the Severn and does not cross the Welsh border. The River Wye is also a major tributary of the Severn, not the main river that holds Britain’s length record.

The Severn has an unusually large tidal range. Its famous Severn Bore is a tidal wave that travels upstream under suitable conditions, making the river notable not only for its length but also for its powerful estuarine tides. The Ironbridge Gorge, an important centre of the early Industrial Revolution, also lies along the Severn.