Weir Wood Reservoir is a 1.5-mile (2.4 km) long stretch of water, situated close to Forest Row, East Sussex, England, on the north-western margins of Ashdown Forest. It has a full water capacity of 5,566,000 cubic metres (1.224×10⁹ imp gal), covering a site of 280 acres (1.1 km²). The reservoir was built over the period 1951-54, a process which involved damming the valley of the River Medway.