Elektrėnai Reservoir (Lithuanian: Elektrėnų marios), located south of the city of Elektrėnai, Lithuania, is the third-largest artificial lake in Lithuania.

It was created in 1961 by damming the Strėva River.

It supplies cooling water to the 1,800 MW Elektrėnai Power Plant.

A number of villages drowned when the reservoir was created; over 140 households were relocated.

The reservoir covers about 1,264 hectares, with depths of over 30 meters.