Pinner is a suburb in the London Borough of Harrow, northwest London, England, 12 miles (19 km) northwest of Charing Cross, close to the border with Hillingdon, historically in the county of Middlesex. The population was 38,698 in 2021.

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.