The Mildmay line is the service operated by London Overground on the North London and West London railway lines. It passes through the inner suburbs of London, between Richmond and Clapham Junction in the south-west and Stratford in the east, avoiding central London. It is one of two London Overground lines to form the outer circle of London linking at Clapham Junction and Highbury and Islington with the Windrush line. Prior to the name being adopted in November 2024, the service was labelled in Transport for London timetables as the Richmond and Clapham Junction to Stratford route.