Derwent Reservoir is the middle of three reservoirs in the Upper Derwent Valley in the north of Derbyshire, England. It lies approximately 10 mi (16 km) from Glossop and 10 mi (16 km) from Sheffield. The River Derwent flows first through Howden Reservoir, then Derwent Reservoir and finally through Ladybower Reservoir. Between them they provide practically all of Derbyshire's water, as well as to a large part of South Yorkshire and as far afield as Nottingham and Leicester.

The Upper Derwent Valley is an area of the Peak District National Park in England. It largely lies in Derbyshire, but its north eastern area lies in Sheffield, South Yorkshire. Its most significant features are the Derwent Dams, Ladybower, Derwent and Howden, which form Ladybower Reservoir, Derwent Reservoir and Howden Reservoir respectively.