Whether you need a passport for St. Martin depends on your nationality and how you arrive. For U.S. Citizens arriving by air, a valid passport is strictly required to enter Princess Juliana International Airport (SXM). Although the island is split between the French side (Saint-Martin) and the Dutch side (Sint Maarten), it is an international destination and does not fall under the same "domestic" rules as Puerto Rico or the U.S. Virgin Islands. If you are a U.S. Citizen on a closed-loop cruise (beginning and ending at the same U.S. port), you may technically be allowed to go ashore with an original birth certificate and a government-issued photo ID, but a passport is still strongly recommended in case of an emergency that requires you to fly home. For 2026 travelers from most other countries, a passport valid for at least six months is standard, and some may require a Schengen visa for the French side or a Caribbean visa for the Dutch side depending on their country of citizenship.