The Porsuk River also Kocasu-Porsuk River (Turkish: Porsuk Çayı, Kocasu-Porsuk Çayı), ancient Tembris, is a river in Turkey, that flows for 448 km. The city of Eskişehir is located on the banks of this river. The river is dammed by the Porsuk dam, forming large reservoirs. The Porsuk flows into the Sakarya River near the town of Polatlı, ancient Gordium.
