The Kolubara is a 87 km (54 mi) long river in western Serbia; it is an eastern, right tributary to the Sava river.

The Sava is a river in Central and Southeast Europe, a right-bank and the longest tributary of the Danube. It flows through Slovenia, Croatia and along its border with Bosnia and Herzegovina, and finally through Serbia, feeding into the Danube in its capital, Belgrade. The Sava forms the main northern limit of the Balkan Peninsula, and the southern edge of the Pannonian Plain.