The Wertach is a river in Bavaria, southern Germany, left tributary of the Lech. Its total length is 151 km. The Wertach originates in the Northern Limestone Alps, in Bad Hindelang, east of Sonthofen (Oberallgäu district). It flows north along the towns Wertach, Nesselwang, Marktoberdorf, Kaufbeuren, Schwabmünchen and Bobingen. The Wertach flows into the Lech (itself a tributary of the Danube) in Augsburg.