The Riley RM Series is an executive car which was produced by Riley from 1945 until 1955. It was the last model developed independently by Riley prior to the 1952 merger of Riley's still new owner Nuffield, with Austin to form BMC. The RM series was originally produced in Coventry, but in 1949 production moved to the MG works at Abingdon. Prior to 1952 models were marketed as the Riley 1½ Litre and the Riley 2½ Litre. the term RM has been used retrospectively to encompass models produced before 1952

Riley was a British motorcar and bicycle manufacturer from 1890. Riley became part of the Nuffield Organization in 1938 and was merged into the British Leyland Motor Corporation in 1968. In July 1969 British Leyland announced the immediate end of Riley production, although 1969 was a difficult year for the UK automotive industry and many cars from Riley's inventory may have been first registered in 1970.