Crummock Water is a lake in Lake District, a national park in the county of Cumbria in the North West of England. Crummock Water is located between Buttermere Lakes on its southern side and Loweswater on its northern side.
Crummock Water is 4 km long, between 500 and 900 m wide and 44 m deep. The Natural Trust is the owner. The lake extends from the northwest to the southeast and is separated from Lake Buttermere by a 1 km long plain. It is believed that both lakes once formed a whole and the land bridge was created by deposits during the last Ice Age. A short river called Buttermere Dubs connects both lakes. In the southeast, the valley is closed by the Fleetwith Pike. Grasmoor Hill is to the northeast and Mellbreak to the southwest.