Ruislip (/ˈraɪslɪp/ RY-slip) is a town in west London, England, which is part of the London Borough of Hillingdon.

It was formerly a parish in the county of Middlesex covering the neighbouring areas of Eastcote, Northwood, Ruislip Manor and South Ruislip. The parish appears in the Domesday Book, and some of the earliest settlements still exist today, designated as local heritage sites. The parish church, St Martin's, dates back to the 13th century and remains in use. The buildings at the northern end of Ruislip High Street form the core of the original village square and are now Grade II listed. It originally featured a central water pump which was moved out of the road in the 1970s as a result of increased traffic.