Koynanagar is a town in Maharashtra, India. It is situated on the Chiplun-Sangli state highway on the banks of Koyna River. The town is small but famous for Koyna Dam and the Koyna Hydroelectric Project which is the largest completed hydroelectric project of India. An earthquake in 1967 flattened the city.

Koyna Nagar is nestled in the Western Ghats, about 746 m (2,448 ft) above sea level, and hence has a tolerable climate for most of the year.