Harlington is a district of the London Borough of Hillingdon, on the northern perimeter of London Heathrow Airport. It is centred west of Charing Cross. The district adjoins Hayes to the north and shares a railway station with the larger district, which is its post town, on the Great Western Main Line.
Harlington is one of the ancient parishes of Middlesex. From 1894 to 1930 it was part of Staines Rural District and from 1930 to 1965 it was part of Hayes and Harlington Urban District. In 1965 civil parishes in the newly-created Greater London were abolished and the former territory of Harlington became part of the London Borough of Hillingdon.