Royal Mail Ship, usually seen in its abbreviated form RMS, is the ship prefix used for seagoing vessels that carry mail under contract to the British Royal Mail. The designation dates back to 1840. Any vessel designated as "RMS" has the right both to fly the pennant of the Royal Mail when sailing and to include the Royal Mail "crown" insignia with any identifying device and/or design for the ship.

The Royal Mail Group Limited, trading as Royal Mail, is a British postal service and courier company. It is owned by International Distributions Services. It operates the brands Royal Mail and Parcelforce Worldwide (parcels). The company used the name Consignia for a brief period in the early 2000s but changed it afterwards.