Harrow is a large town in Greater London, England, and serves as the principal settlement of the London Borough of Harrow. Lying about 9.5 miles (15.3 km) north-west of Charing Cross and 5.4 miles (8.7 km) south of Watford, the entire town including its localities had a population of 149,246 at the 2011 census, whereas the wider borough had a population of 250,149.

The London Borough of Harrow is a London borough in northwest London, England; it forms part of Outer London. It borders four other London boroughs – Barnet to the east of ancient Watling Street, Brent to the southeast, Ealing to the south and Hillingdon to the west – plus the Hertfordshire districts of Three Rivers and Hertsmere to the north. The local authority is Harrow London Borough Council. The London borough was formed in 1965, based on boundaries that had been established in 1934. The borough is made up of three towns: Harrow, Pinner and Stanmore, but also includes western parts of Edgware.