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.

RMS Amazon was a transatlantic Royal Mail Ship that the Royal Mail Steam Packet Company operated on scheduled services between Southampton and South American ports including Buenos Aires. She was the second of the RMSP's fleet of "A" series liners, and was launched in 1906.