The Weser 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 50 km (31 mi) 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.

The Main is the longest tributary of the Rhine. It rises as the White Main in the Fichtel Mountains of northeastern Bavaria and flows west through central Germany for 525 kilometres (326 mi) to meet the Rhine below Rüsselsheim, Hesse. The cities of Mainz and Wiesbaden are close to the confluence.