The Nieuwe Maas ("New Meuse") is a stretch of river in the Netherlands, taking water from the Rhine and the Meuse. It begins at the intersection of rivers Noord and Lek and flows west through Rotterdam. It continues until its confluence with the Oude Maas near the city of Vlaardingen. Here, the Nieuwe Maas originally forked into two branches, with river Het Scheur flowing westward and the Nieuwe Maas continuing southwest to the town of Den Briel, where the Scheur and Nieuwe Maas branches flowed together again to form the Brielse Maas estuary. The last stretch of Nieuwe Maas was dammed off, however, at the Botlek strait, and all of its water is now discharged through Het Scheur. The total distance nowadays is approximately 24km.

Although this branch is called "Maas" (Meuse), it gets most of its water from river Rhine, of which it is an important estuary.

Connections between the mainland on the north and IJsselmonde island on the south, from west to east:

• 1st and 2nd Benelux Tunnel (motor vehicles, cyclists and metro)
• Maas Tunnel (motor vehicles, cyclists, pedestrians)
• Erasmus Bridge (motor vehicles, cyclists, pedestrians, trams)
• metro tunnel
• Willems Tunnel (trains)
• Willems Bridge (motor vehicles, cyclists, pedestrians)
• Van Brienenoordbrug (motor vehicles, cyclists, pedestrians)