Tervakoski (; ) is a small town in Janakkala, Finland. In 2021, there were 3,972 inhabitants.
A well-known and popular amusement park Puuhamaa is located in the village. About southeast of Puuhamaa, on the other shore of , is Tervaniemi, which offers accommodation.
Tervakoski Oy's paper mill, established in 1818, is located in Tervakoski.