The Nieuwe Merwede ("New Merwede") is a canal that was constructed in 1870 to form a branch in the Rhine-Meuse delta. It was dug along the general trajectories of a number of minor Biesbosch creeks to reduce the risk of flooding by diverting the water away from the Beneden Merwede, and to facilitate navigation and regulate river traffic in the increasingly silted-up delta.
It is one of several rivers called Merwede. The river Boven Merwede ("Upper Merwede"), itself the continuation of the Rhine-Waal and Meuse (now Afgedamde Maas) rivers after their confluence at Gorinchem, branches near the town of Hardinxveld-Giessendam into River Beneden Merwede ("Lower Merwede") to the northwest and the Nieuwe Merwede to the southwest. The Nieuwe Merwede joins River Bergse Maas near Lage Zwaluwe to form the Hollands Diep estuary, and separates the Island of Dordrecht from the Biesbosch National Park.