Fox Hagg is a small (33.25 hectares (82.2 acres)) nature reserve in the Rivelin Valley area of Sheffield, England.[1] The Allen Sike flows along the north edge of the reserve and the River Rivelin flows through the reserve from Rivelin Dams to the west. The Wyming Brook Nature Reserve borders Fox Hagg to the west.[2] The site is managed by the Wildlife Trust for Sheffield and Rotherham.[3]