Royal Caribbean International is a cruise line brand founded in Norway and based in Miami, Florida, United States. It is owned by Royal Caribbean Cruises Ltd. As of March 2017, the line is operating 25 ships, has six additional ships on order, and controls 21.9 percent of the cruise market worldwide. All ships under the Royal Caribbean International brand have names ending with \"of the Seas\" (e.g. Empress of the Seas) a practice which began in 1991. Sister brands owned by Royal Caribbean Cruises Ltd. are Celebrity Cruises, Azamara Cruises, Pullmantur Cruises and CDF Croisières de France.