Farmoor Reservoir is a reservoir at Farmoor, Oxfordshire, England, about 5 miles (8 km) outside the city of Oxford. It is close to the left bank of the River Thames. Like most of the reservoirs in the Thames Valley, it was not formed by damming a valley. In this case the banks were raised above the local ground level using material excavated from within the bowl of the reservoir.
The reservoir is split into Stage 1 (completed 1967, 4,544 million litres) and Stage 2 (completed 1976, 9,298 million litres). Among other locations, Farmoor supplies the large town of Swindon, some 25 miles (40 km) to the southwest. The reservoir is filled from the River Thames.
The reservoir is used for sports: fishing (especially fly-fishing for rainbow and brown trout), dinghy sailing and windsurfing. Oxford Sailing Club and the Oxford and District School Sailing Association are based there). There is also access for bird watching and walking.