Royal yacht
A royal yacht is a vessel commissioned for the exclusive use of a monarch or a royal family. If the monarch is an emperor the proper term is imperial yacht. Most of them are financed by the government of the country of which the monarch is head. The royal yacht is most often crewed by personnel from the navy and used by the monarch and their family on both private and official travels.
While some historical examples were privately funded, the majority of modern royal yachts are financed and maintained by the government of the country the monarch rules.