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.
Read more about this topic: Her Majesty's Ship