The Weser (ˈveːzɐ) is a river of Lower Saxony in north-west Germany. It begins at Hannoversch Münden through the confluence of the Werra and Fulda. It passes through the Hanseatic city of Bremen. Its mouth is further north against the ports of Bremerhaven and Nordenham. The latter is on the Butjadingen Peninsula. It then merges into the North Sea via two highly saline, estuarine mouths.
It connects to the canal network running east-west across the North German Plain.
The river, when combined with the Werra (a dialectal form of Weser), is long and thus, the longest river entirely situated within Germany (the Main, however, is the longest if the Weser and Werra are not combined). The Weser itself is long. The Werra rises in Thuringia, the German state south of the main projection (tongue) of Lower Saxony.
"Weser" and "Werra" are the same words in different dialects. The difference reflects the old linguistic border between Central and Low German, passing through Hannoversch Münden.
The name likely derives from the Old Germanic *waisōn "flow, ooze". It is cognate with the Wear in England and Vistula (Polish Wisła, German Weichsel) in Poland, all of which are derived from the Proto-Indo-European root *weys- "to flow", which also gives rise to Old English/Old Frisian wāse "mud, ooze", Old Norse veisa "slime, stagnant pool", Dutch waas "haze; soggy land" (see Waasland), Old Saxon waso "wet ground, mire", Old High German wasal "rain" and French vase "mud, sludge".
The Weser starts at the confluence of the Fulda and the Werra. It then runs down to the Porta Westfalica between two high hill ranges, the Wiehengebirge, west and the Weserbergland in the east.
Between Minden and the North Sea, humans have largely canalised the river up to a limit of 1,200-ton ships. Eight hydroelectric dams stand at the ends of adjacent weirstreams that make up the river. The navigation is linked west to the Dortmund–Ems Canal via the Coastal Canal. It is linked east at Bremerhaven to the Elbe.