TSS (RMS) Mona's Queen (III) No. 145308, was a ship built for the Isle of Man Steam Packet Company in 1934. The steamer, which was the third vessel in the company's history to bear the name, was one of five ships to be specially commissioned by the company between 1927 and 1937. They were replacements for the various second-hand steamers that had been purchased to replace the company's losses during the First World War. However, the life of the Mona's Queen proved to be short: six years after being launched she was sunk by a sea mine during the Dunkirk evacuation on 29 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.