Northwood is an area in the London Borough of Hillingdon, North West London, located 14.5 miles (23.3 km) north-west of Charing Cross. Northwood was part of the ancient parish of Ruislip, Middlesex. The area was situated on the historic Middlesex boundary with Hertfordshire, and since being incorporated into Greater London in 1965, has been on the Greater London boundary with that county.

The London Borough of Hillingdon is the largest and westernmost borough in West London, England. It was formed in 1965 from the districts of Hayes and Harlington, Ruislip-Northwood, Uxbridge, and Yiewsley and West Drayton in the ceremonial county of Middlesex. Today, Hillingdon is home to Heathrow Airport and Brunel University, and is the second largest of the 32 London boroughs by area.