Wraysbury Reservoir is a water supply reservoir for London, just west of the M25 near the village of Wraysbury, and directly under the western approach path of Heathrow Airport.

[4] The reservoir is owned and operated by Thames Water; 400 million litres (100 million gallons) of water are pumped daily from an inlet at Datchet on the River Thames.

To keep the grass short and make inspections easier, Thames Water maintains a flock of sheep on the earthen banks.

[5] The reservoir is the site of the National Physical Laboratory's Open-Water Test Facility, used by the Ministry of Defence for test and calibration of sonar systems, as well as civilian commercial customers.

[9] It has nationally important numbers of wintering cormorants, great crested grebe and shovelers.