Torside Reservoir is the largest man-made lake in Longdendale in north Derbyshire, England.

It was constructed by John Frederick Bateman between April 1849 and July 1864 as part of the Longdendale Chain of reservoirs to supply water from the River Etherow to the urban areas of Greater Manchester.

c. cciii) gave permission for the construction of the Woodhead and Arnfield reservoirs; the Manchester Corporation Waterworks Act 1848 allowed the construction of Torside and Rhodeswood Reservoirs, and an aqueduct to convey the water to the Arnfield reservoir where it would pass through the Mottram Tunnel to Godley.

Woodhead, as the fountainhead, would require the most extensive improvements, but Torside needed crest remedial work.

The wave wall was demolished and replaced with one 4 metres (13 ft) above the overflow sill.