Harwell is a village and civil parish in the Vale of White Horse about 2 miles (3 km) west of Didcot, 6 miles (10 km) east of Wantage and 13 miles (21 km) south of Oxford. The parish measures about 3.5 miles (6 km) north – south, and almost 2 miles (3 km) east – west at its widest point. In 1923 its area was 2,521 acres (1,020 ha). Historically in Berkshire, it has been administered as part of Oxfordshire, England, since the 1974 boundary changes. The parish includes part of Harwell Science and Innovation Campus in the southwest. The 2011 census recorded the parish's population as 2,349.

The Rutherford Appleton Laboratory (RAL) is one of the national scientific research laboratories in the UK operated by the Science and Technology Facilities Council (STFC). It began as the Rutherford High Energy Laboratory, merged with the Atlas Computer Laboratory in 1975 to create the Rutherford Lab; then in 1979 with the Appleton Laboratory to form the current laboratory.