The Wertach is a river in Bavaria, southern Germany, a left tributary of the Lech. Its total length is . The Wertach originates in the Northern Limestone Alps in Bad Hindelang, east of Sonthofen (district Oberallgäu). 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.