The Iskar Reservoir (язовир „Искър“) is the largest reservoir in Bulgaria. It is situated on the Iskar River and provides 2/3 of the water for the capital Sofia, also being used for producing hydroelectricity.
The reservoir has a total volume of 673 million m3, of which 580 million are in use and the rest is reserve. The reservoir has a drainage basin of 1,046 km² and is 25 km long. It is situated at 820 m above sea level, its dam being 204 m long and 76 m high.