Her Majesty's Ship

Her or His Majesty's Ship (HMS) is the ship prefix used for ships of the navy in some monarchies, either formally or informally.

Sweden

In the Swedish Navy (formerly the Royal Swedish Navy), all vessels are given the prefix HMS (Hans or Hennes Majestäts Skepp). This is true for both surface and submarine vessels.

Abroad, Swedish navy ships are sometimes given the prefix HSwMS (for His Swedish Majesty's Ship), this in order so that any confusion with other uses of HMS can be avoided.

United Kingdom

In the British Royal Navy, the prefix was originally always quoted in full; the first recorded use of the abbreviated form, "HMS", was in 1789 in respect of HMS Phoenix. Formerly, HBMS (for His or Her Britannic Majesty's Ship) was also used.

Submarines in Her Majesty's service have the prefix HM Submarine. Similarly, the Royal Yacht Britannia, which was a commissioned ship in the Royal Navy, was known as HMY Britannia. 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 Frigate X, or HM Sloop Y.