London Buses route 427 is a Transport for London contracted bus route in London, England. Running between Uxbridge and Southall, it is operated by Transport UK London Bus.

Uxbridge is a suburban town in west London and the administrative headquarters of the London Borough of Hillingdon. Situated 15.4 miles (24.8 km) west-northwest of Charing Cross, it is one of the major metropolitan centres identified in the London Plan. Uxbridge formed part of the parish of Hillingdon in the county of Middlesex, and was a significant local commercial centre from an early time. As part of the suburban growth of London in the 20th century it expanded and increased in population, becoming a municipal borough in 1955, and has formed part of Greater London since 1965.