The Lahn River is a 245.6-kilometer (152.6 mi)-long, right (or eastern) tributary of the Rhine River in Germany. Its course passes through the federal states of North Rhine-Westphalia (23.0 km), Hesse (165.6 km), and Rhineland-Palatinate (57.0 km).It has its source in the Rothaargebirge, the highest part of the Sauerland. It meets the Rhine at Lahnstein, near Koblenz.