Küçük Menderes, "Little Meander"), Cayster River or Kaystros River is located south of İzmir, Turkey. The Cayster generally flows westward and arrive into the Aegean Sea at Pamucak beach near Selçuk, İzmir. The ancient city of Ephesus was once an important port on the Cayster, but over the centuries, sedimentation gradually filled in the inlet around the city. The coastlines moved seaward and the ruins of Ephesus are now some 5 miles (8.0 km) inland from the coast.
The tributaries are the Fertek, Uladı, Ilıca, Değirmen, Aktaş, Rahmanlar, Prinçci, Yuvalı, Ceriközkayası, Eğridere, Birgi, Çevlik and Keles.