The Kostroma (Russian: Кострома́) is a river in the European part of Russia. It flows through the Kostroma and Yaroslavl Oblasts, and becomes a left tributary of the Volga, which it enters at the Gorky Reservoir, at the city of Kostroma.
Prior to the flooding of the Gorky Reservoir in 1955-1957, the Kostroma River flowed into the Volga within the city limits of Kostroma. The Ipatiev Monastery stands at the old confluence of the Kostroma and the Volga.
The river is 354 kilometres long, and its drainage basin covers 16,000 square kilometres. The average water flow is 71 cubic metres per second at the town of Buy, 124 kilometres from the mouth, and 85 cubic metres per second at the mouth.
