No, for a Carnival cruise in 2026, you generally cannot use a photocopy of a birth certificate. To board a "closed-loop" cruise (one that begins and ends at the same U.S. port) without a passport, U.S. citizens must present an original state-issued birth certificate or a certified copy—which is an official document issued by the government with a raised seal or multicolored signature. Hospital-issued "souvenir" certificates with baby footprints are not accepted. Carnival's 2026 policy strictly states that "photocopies of required documentation are not acceptable in any circumstance." If you do not have a valid passport, you must also provide a government-issued photo ID (such as a driver's license) if you are 16 or older. It is highly recommended to travel with a passport regardless, as a birth certificate will not allow you to fly back to the U.S. from a foreign port in the event of an emergency or if you miss the ship's departure.