His (orHer)Majesty's Ship, abbreviatedHMS andH.M.S., is theship prefix used for ships of the navy in some monarchies. Derivative terms such asHMAS and equivalents in other languages such asSMS are used.

With regard to the separateEnglish andScottish navies of the medieval period andearly modern era, historians usually use terms such as "English Ship" or "Scottish Ship".[citation needed]
During the late 17th century, followingthe Restoration, the name Royal Navy was officially adopted, as well as the prefix His Majesty's Ship, and later, Her Majesty's Ship.[citation needed] The first recorded use of the abbreviated form HMS was in 1789, in respect ofHMSPhoenix.[1]From 1707 to circa 1800HBMS (forHis Britannic Majesty's Ship) was also used.[2][3]Submarines in His Majesty's service also use the prefix HMS, standing forHis Majesty's Submarine, though this is sometimes renderedHMS/m.[4] (See, for example,HMS/mTireless, atIWM). TheRoyal YachtBritannia, which was a commissioned ship in the Royal Navy, was known as HMYBritannia. Otherwise all ships in the Royal Navy are known as HM Ships, though formerly when a distinction was made between three-masted ship-rigged ships and smaller vessels they would be called HM FrigateX, or HM SloopY.
The prefix HMS is also used by shore establishments that are commissioned "stone frigates" in the Royal Navy. Examples includeHMSExcellent, a training school located on an island inPortsmouth Harbour, andHMSVulcan, inCaithness in theHighland area ofScotland, which is established to test the design ofnuclear power systems for use in submarines.
The sample ship name used by theRoyal Navy to signify a hypothetical vessel isHMS Nonsuch.[5] Thisis a name that has been used by theRoyal Navy in the past; on the eve ofWorld War II the name was given[by whom?] to theRoyal Canadian Navy. As of 2012[update]HMCSNonsuch was the "stone frigate" of the Edmonton Division of theCanadian Naval Reserve.[6]
Prefixing the name by "the", as in "the HMS Ark Royal", while common, is considered bad grammar.[7]
British government ships not in the Royal Navy have other designations, such asRFA for ships in theRoyal Fleet Auxiliary.
Historically, variants on HMS have been used by the navies of British colonies. The practice is maintained in severalCommonwealth realms – states in which the monarch of the UK is head of state – as well asother Commonwealth countries and former members of theBritish Empire.
AllDanish Navy ships carry the ship prefixKDM (Kongelige Danske Marine) in Danish, but this is translated toHDMS (Her / His Danish Majesty's Ship) in English.
Seiner Majestät Schiff (pronounced[ˈzaɪnɐmajɛsˈtɛːtʃɪf];German for 'His Majesty's Ship'; abbreviated toS.M.S. orSMS) was theship prefix used by the PrussianMaritime Enterprise (Seehandlung), thePrussian Navy, theImperial German Navy (Kaiserliche Marine) and theAustro-Hungarian Navy (Kaiserliche und königliche Kriegsmarine). It was created by translating the British prefix into German.
It was sometimes also abbreviated toS.M. orSM (forSeiner Majestät) when a ship was mentioned by class, such asS.M. Kleiner Kreuzer Emden ("His Majesty's Light Cruiser Emden").
Special forms included
International prefixes for ships of theRoyal Netherlands Navy isHNLMS (His/Her Netherlands Majesty's Ship).[25] The Netherlands navy itself uses the prefixesZr.Ms. (Zijner Majesteits,His Majesty's) when a king is on the throne, andHr.Ms. (Harer Majesteits,Her Majesty's) when there is a queen. Changes happen automatically at the beginning of a new monarch's reign.[26]
TheRoyal Norwegian Navy vessels have since 1946 been given theship prefixKNM, short forKongeligNorskeMarine (Royal Norwegian Navy). InEnglish, they are given the prefixHNoMS, short for "His/HerNorwegianMajesty'sShip" (HNMS could be also used for theRoyal Netherlands Navy, for whichHNLMS is used instead). Coast Guard vessels are given the prefixKV forKystVakt (Coast Guard) inNorwegian andNoCGV forNorwegianCoastGuardVessel in English.
Prior toWorld War II, the subsequent ousting of themonarchy of Romania on 30 December 1947 and post-warSoviet occupation, allRoyal Romanian Navy vessels were given the prefixNMS which stands forNava Majestăţii Sale which translates toHis/her Majesty's Ship in English.
In theRoyal Swedish Navy, all vessels are given the prefix HMS (Hans orHennes Majestäts Skepp,His orHer Majesty's Ship). This is true for both surface and submarine vessels.[27]
Abroad, Swedish navy ships are sometimes given the prefixHSwMS (forHis Swedish Majesty's Ship), to avoid confusion with other uses of the HMS prefix.[27]
In theRoyal Thai Navy, ships with a displacement of 150 tons or more use the prefix เรือหลวง ("Royal Ship"), abbreviatedร.ล. meaning ships belonging to theThai King. In English, the abbreviationHTMS orH.T.M.S. comes from the wordHis Thai Majesty's Ship.[28] For the name of the ship, it must be granted by the King.[28][29]
In theTongan Maritime Force, commissioned ships use the prefixVaka O Ene Afio, abbreviated "VOEA", meaning "His Majesty's Vessel" inTongan. The initialism is usually left untranslated in English.
Some, but apparently not all, other navies also use prefixes with their ships' names. Perhaps the best known of these is HMS (His/Her Majesty's Ship), long used by the Royal Navy. In earlier times this was also seen asHBMS forHis Britannic Majesty's Ship.