The Thur is a 135-kilometre-long (84 mi) river in north-eastern Switzerland and a tributary of the High Rhine (Hochrhein).

The name has been interpreted as an Old European hydronym, from *durâ or *duriâ “river” from the Indo-European root *dhu “to run, to hurry”.

The river's source is near Wildhaus in the south-east of the Toggenburg region in the canton of St. Gallen, south of Säntis mountain (Alpstein).

Close to the town of Wil, it turns eastward and the Thur[3] continues through the canton of Thurgau, which is named after the river.

North of Flaach, it then flows into the River Rhine (High Rhine) near the border between the canton of Zürich and the southern part of the canton of Schaffhausen (Rüdlingen-Buchberg), just a short distance south of the border with Germany.