Hammergraben

51°51′16″N 14°15′39″E / 51.8544°N 14.2608°E / 51.8544; 14.2608Basin featuresProgressionGroßes Fließ→ Spree→ Havel→ Elbe→ North Sea

Hammergraben is a river of Brandenburg, Germany. It branches off the Spree in Cottbus, and flows into the Großes Fließ (a tributary of the Spree) in Schmogrow-Fehrow. It is used to flood Cottbuser Ostsee, a former open pit lignite mine, which is planned to become Germany's largest artificial lake by surface area.

• List of rivers of Brandenburg