||This article does not cite any sources. (December 2009)
The Oster River (Ukrainian: Остер) is a river in the northern Ukrainian oblast of Chernihiv. The river is the left branch of the Desna River. It is approximately 199 km long and its basin area is 2,950 km². It is connected by canals and streams with the Trubizh River, which flows southwest from Kiev into the Dnieper River. Important towns and villages on the river include: Nizhyn, Kozelets, Roslavl and Oster.
Coordinates: 50°56′10″N 30°50′52″E / 50.936°N 30.8478°E