Käsmu (German: Kaspervik, Hasterwieck) is a village in Haljala Parish, Lääne-Viru County, in northern Estonia, on the territory of Lahemaa National Park. It's located northwest of Võsu, on the Käsmu Peninsula in the Gulf of Finland, surrounded by the Eru Bay to the west and the Käsmu Bay to the east.
Käsmu was first mentioned in 1453 as Kesemo, a beach belonging to the Aaspere Manor. Later in 1524 it is affirmed that Käsmu exists as a village. Due to the location the food was mostly acquired from the sea. Main fishes included Baltic herring and flounder.