Weser (vāˈzər) [key], river, c.300 mi (480 km) long, formed at Hannoversch-Münden, central Germany, by the junction of the Fulda and Werra rivers. It flows generally N past Minden, where it passes through the Porta Westphalia into the North German plain. It enters the North Sea through a long estuary N of Bremen. The Hunte and Aller rivers are among its chief tributaries. Navigable to Kassel on the Fulda River, the Weser is connected by the Midland canal system with the Rhine, the Ems, and the Elbe rivers.