Lopasnya

General data
- Name: Lopasnya
- Basin: Volga
- Water type: River
- Progression: Oka -> Volga -> Caspian Sea -> Planet Earth
- Climates: Continental
- Continents: Europe
- Countries: Russia
Description
The Lopasnya (Russian: Лопа́сня) is a river in Moscow Oblast in Russia. It is a left tributary of the Oka. It is 108 km in length, with a drainage basin of 1090 km². Its average discharge is 6,76 m³/s.