In 2026, whether you can use a REAL ID instead of a passport for a cruise depends entirely on the itinerary type. For "Closed-Loop" cruises—those that begin and end at the same U.S. port and stay within the Western Hemisphere (e.g., Caribbean, Bahamas, Mexico)—U.S. citizens can still use a combination of a REAL ID (or standard Driver's License) AND an original birth certificate. However, a REAL ID alone is not sufficient for international sea travel; it only proves identity, not citizenship. For any "Open-Loop" cruise (one that starts in one city and ends in another) or any international sailing beginning in a foreign port like Vancouver or Barcelona, a valid passport is mandatory in 2026. Cruise lines like Royal Caribbean and Carnival strongly recommend a passport even for closed-loop sailings, as it is the only document that allows you to fly home from a foreign port in the event of a medical emergency or a missed ship.