Ogosta Reservoir, Artificial reservoir in Montana region, Bulgaria.

Ogosta Reservoir is an artificial lake in north-west Bulgaria, fourth in area and second in volume among the country's artificial water bodies. It collects the waters of the Ogosta, Burzia and Zlatitsa rivers and lies 600 metres south-west of the edge of Montana, 60 metres above the city's level. Its catchment covers 948 km² and the lake itself 23.6 km², with an average volume of 384 million m³.

The reservoir was created by constructing a dam over several decades, which flooded two villages in the process. Residents from the submerged settlements relocated to nearby towns including Berkovitsa and Montana.

The name Ogosta may derive from the Latin Augusta, as suggested by the Cambridge Ancient History. Two villages, Jivovtsi and Kalimanitsa, were submerged when the reservoir filled; Jivovtsi was the birthplace of writer and artist Ivan Davidkov and poet Anastas Stoyanov, and Kalimanitsa of writer Yordan Radichkov.

You can approach the reservoir from several points around the Montana region and view it from multiple vantage spots. Note that two hydroelectric power stations operate downstream, so access to certain areas may be restricted.

Beyond being a water body, the reservoir has become a center for commercial fishing operations that began in the late 20th century. This activity has grown into an important economic element for surrounding communities.