Seiner Majestät Schiff

Seiner Majestät Schiff (German: "His Majesty's Ship", abbreviated to S.M.S. or SMS) was the ship prefix used by the Prussian Maritime Enterprise (Seehandlung), the Prussian Navy, the Imperial German Navy (Kaiserliche Marine) and the Austro-Hungarian Navy. It was created by translating the British prefix Her Majesty's Ship ("HMS") into German.

It was sometimes also abbreviated to S.M. or SM (for Seiner Majestät) when a ship was mentioned by class, such as S.M. Kleiner Kreuzer Emden ("His Majesty's Light Cruiser Emden").

Special forms included
 * S.M.Y. (or SMY)=Seiner Majestät Yacht ("His Majesty's Yacht") for king's or emperor's yacht
 * I.M.Y. = Ihrer Majestät Yacht ("Her Majesty's Yacht") for the queen's or empress's yacht.
 * S.M.F. = Seiner Majestät Feuerschiff ("His Majesty's Lightvessel")
 * S.M.H. = Seiner Majestät Hilfsschiff ("His Majesty's Auxiliary Ship")
 * S.M.W. = Seiner Majestät Werkstattschiff ("His Majesty's Workshop Ship")
 * S.M.U. = Seiner Majestät Unterseeboot ("His Majesty's Submarine", prefixing a number not a name)