Diamond Princess is a British-registered cruise ship owned and operated by Princess Cruises. She began operation in March 2004 and primarily cruises in Asia during the northern hemisphere summer and Australia during the southern hemisphere summer. She is a subclassed Grand-class ship, which is also known as a Gem-class ship. Diamond Princess and her sister ship, Sapphire Princess, are the widest subclass of Grand-class ships, as they have a 37.5-metre beam, while all other Grand-class ships have a beam of 36 metres. Diamond Princess and Sapphire Princess were both built in Nagasaki, Japan, by Mitsubishi Industries.

Princess Cruises is an American cruise line owned by Carnival Corporation & plc. The company is incorporated in Bermuda and its headquarters are in Santa Clarita, California. As of 2021, it is the second largest cruise line by net revenue. It was previously a subsidiary of P&O Princess Cruises. The line has 15 ships cruising global itineraries that are marketed to both American and international passengers.