Sulby Reservoir, reservoir on the Isle of Man

Sulby Reservoir is the largest lake on the Isle of Man, covering 154 acres (62 ha) at the head of Sulby Glen near the source of the Sulby River. Its rock-fill embankment dam stands 73 metres (240 ft) high and was completed in 1982. The reservoir holds 4,832,000 cubic metres of water and reaches a maximum depth of 73 metres.

Reservoirs were built on the Isle of Man from the 19th century to meet rising demand for drinking water, and until 1948 nine municipal and commercial companies ran them. The Isle of Man Water Board was formed that year. A reservoir in the Sulby valley was decided in 1976, approved in 1979, and the dam was built in two stages, to 35 m then 60 m, finished in August 1982; filling reached the design level in April 1983.

The reservoir lies at the top of Sulby Glen, about 1.5 miles (2.4 km) west of Snaefell's summit, at the meeting point of the parishes of Michael, Lezayre and Braddan. A large car park serves visitors, and trout fishing is available. The site is a registered dark sky discovery site, so night visits are worthwhile.

Sulby Reservoir is a registered Dark Sky Discovery site, so stargazers can observe from the large car park beside the water. The reservoir lies about 1.5 miles (2.4 km) west of Snaefell, the island's highest peak, and anglers can fish for trout there.