The Bolshaya Kokshaga (Mari:Кугу Какшан, Kugu Kakšan; Russian:Больша́я Кокша́га, literally Great Kokshaga) is a river in Kirov Oblast and Mari El, Russian Federation. It is a left-bank tributary of the Volga. Its length is 297 km and its drainage basin is 6,330 km². The river is fed by snow and rain, and from November till April it is usually frozen.