Yes, Lawful Permanent Residents (LPRs) of the U.S. can go on Carnival Cruises in 2026, but the documentation requirements vary by route. For "Closed-Loop" cruises (starting and ending in the same U.S. port), you generally only need your valid I-551 (Green Card) for re-entry into the United States. However, it is a crucial 2026 supportive tip to carry your passport from your country of citizenship as well. This is because while the U.S. might let you back in with just a Green Card, specific destination countries in the Caribbean or Central America may require a passport—and sometimes a visa—to disembark. Additionally, in the event of an emergency (like a medical evacuation) that requires you to fly back to the U.S. from a foreign country, a passport is legally required for air travel. Always ensure your Green Card is not expired, as expired cards will prevent you from boarding.