Southdown Motors Services Ltd (although this was the legal name of the company (until 1992) it was normally referred to as Southdown Motor Services) was a bus and coach operator in East and West Sussex and parts of Hampshire, in southern England. It was formed in 1915 and had various owners throughout its history, being purchased by the National Bus Company (NBC) in 1969. The company fleet name was lost when it was acquired by the Stagecoach Group in 1989 but buses operated under that legal name until 2015 when the operating licence was transferred to another company within the Stagecoach Group and 1915 company became dormant but still owned by the Stagecoach Group.