The Weser is a river of north-western Germany. Formed at Hannoversch Münden by the joining of the Fulda and Werra rivers, it flows through Bremen to the North Sea, and has a length of 440 km. Together with the Werra, its length is 730 km.

The top section of the river's course leads through a hilly region called the Weserbergland. It extends from the confluence of Fulda and Werra to the Porta Westfalica, where the Weser runs through a gorge between two mountain chains, the Wiehengebirge in the west and the Wesergebirge in the east.

Between Minden and the North Sea, the Weser has largely been canalised, permitting ships of up to 1,200 tons to navigate the river. Eight hydroelectric dams are located along its length. Further downstream, the river is linked to the Dortmund-Ems canal via the Küsten canal, and another canal links the river at Bremerhaven to the Elbe River. A large reservoir on the Eder river, a major tributary of the Fulda, is used to regulate water levels on the Weser so as to ensure adequate depth for shipping throughout the year. The dam, built in 1914, was torpedoed and destroyed by British planes in February 1943, causing massive loss of life and destruction downstream, but was rebuilt soon after. Today, the reservoir (Edersee) is a major summer resort area and provides substantial hydroelectricity.

Towns along the Weser, from the confluence of Werra and Fulda to the mouth are: Hannoversch Münden, Beverungen , Höxter , Holzminden, Bodenwerder, Hamelin, Hessisch-Oldendorf , Rinteln, Vlotho, Bad Oeynhausen , Porta Westfalica, Minden, Petershagen , Nienburg, Achim , Bremen, Brake , Nordenham, Bremerhaven.

The largest tributary of the Weser is the Aller river, which joins the Weser south of Bremen.

Tributaries of Weser and Werra (from source to mouth):

• Left
  • Ulster
  • Fulda
  • Diemel
  • Große Aue
  • Hunte
• Right
  • Nesse
  • Aller
  • Lesum (Wümme)