TSS (RMS) King Orry (IV) - the fourth vessel in the line's history to be so named - was the lead ship of the King Orry Class of passenger ferries and packet ships. More commonly referred to as the six sisters, they were built for the Isle of Man Steam Packet Company between 1946 & 1955 primarily to replace war-time losses. The company's previous King Orry was one of three company losses during Operation Dynamo - the evacuation of British and French troops from the port of Dunkirk during May 1940.

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.