The Töss is a river in the Swiss canton of Zürich and a tributary of the High Rhine (Hochrhein).

It starts at Tössscheidi, the confluence of the Vordertöss and Hindertöss (whose sources are in the canton of St. Gallen), passes through Winterthur's Töss and Wülflingen districts and ends at Tössegg near Freienstein-Teufen.

The Hintertöss passes Tössstock on its northern hillside before joining the Vordertöss at Tössscheidi.

The Töss continues south of Eschenberg mountain, Winterthur's Hausberg, before reaching its confluence with the River Kempt.

After joining the River Eulach on the western end of Winterthur, the Töss continues for about 11 kilometres (6.8 mi) in a more or less westnorthwestern direction and finally joins the High Rhine at Tössegg, west of Teufen.

At Tössegg, the Rhine bends sharply towards northwest, passing the village of Tössriederen, and continues westwards again before flowing through Eglisau.

Related toponyms are documented earlier, such as Tössegg (locum dictum Tossegge, 1216), Tössriederen (apud Tossriedern, 1277), and the name "Tösser" (dicti Tösserre, 1267).