It is 31 mi (50 km) long and rises on Dartmoor, becomes an estuary just below Newton Abbot and reaches the English Channel at Teignmouth.

[2] The second source rises near Grey Wethers and forms the shorter South Teign which flows through the Fernworthy Forest and a reservoir of the same name.

The two rivers combine at Leigh Bridge near Chagford to form the Teign, which leaves the moor on its eastern side, flowing beneath Castle Drogo in a steep-sided valley.

Below Newton Abbot the river turns abruptly to the east and becomes tidal, widening to form the Teign Estuary, a large ria that reaches the English Channel at Teignmouth.

The port of Teignmouth, just inside the mouth of the estuary, is visited by ships mostly handling clay, timber and grain.

The lower reaches of the river are navigable up to Newton Abbot, although now only to shallow draft boats and those less than 2.9 metres high due to the Shaldon Bridge.

[7] The tidal Whitelake Channel of the river connects it to two disused short canals that were both built to serve the ball clay trade in the area.