The Riß is a small river in Baen-Württemberg, south-western Germany, right tributary of the Danube. Its source is in Upper Swabia, between Bad Waldsee and Bad Schussenried. It flows north, through Biberach an der Riß. The Riß flows into the Danube between Ehingen and Erbach, approx. 20 km upstream from Ulm. Its total length is approximately 50 km.