Quality Line was a bus company based in Epsom, England. A subsidiary of the RATP Group, Quality Line operated bus services throughout the South West London and Surrey area, with many under contract to Transport for London. It ceased operations on 2 July 2021, with all remaining routes transferring to RATP's London United subsidiary.

RATP Dev Transit London Limited, trading as RATP Dev Transit London, is a bus company operating mostly in west and south-west Greater London. The London United brand is a subsidiary of RATP Dev Transit London and operates services under contract to Transport for London.