Arnfield Reservoir is a man-made lake in Longdendale in north Derbyshire. It was constructed in 1854 as part of the Longdendale chain to supply water from the River Etherow to the urban areas of Greater Manchester. Unlike the other reservoirs in the chain, Arnfield and Hollingworth Reservoir are not in the Etherow valley but lie in the valley of tributary brooks to the north and above (Arnfield lies around 1 mile from Bottoms Reservoir in the Longdendale Chain).