The River Thurso (Scottish Gaelic: Abhainn Theòrsa) has Loch Rumsdale in Caithness as its source, about 26 kilometres (16 mi) south[1] and 14 kilometres (8.7 mi) west of the burgh of Thurso, Caithness, and about 2 kilometres (1.2 mi) south of the railway line linking the burghs of Thurso and Wick with Inverness.
From Loch Rumsdale the river flows generally east/southeast across about 4 kilometres (2.5 mi) until it is joined by Glutt Water, and then generally northeast across about 7 kilometres until it enters the southern end of Loch More.
Whilts there is a small harbour at the river mouth, the main port is now at Scrabster, just to the west.
About 6 kilometres (3.7 mi) further south it is bridged by the rail link connecting both burghs with Inverness.
The river is designated as a special area of conservation due to its "higher proportion of multi sea-winter salmon Salmo salar than is found in many rivers further south in the species’ range.