Yes, U.S. citizens absolutely need a valid passport to enter Saint-Barthélemy (St. Barts) in 2026. As a French Overseas Collectivity, St. Barts sits outside the Schengen Area, meaning that even travelers arriving from other Caribbean islands or Europe must present a passport valid for at least six months beyond their date of departure. The document must also have at least one blank page for an entry stamp. While U.S. citizens do not need a visa for stays under 90 days, the "passport-only" rule is strictly enforced by airlines and ferry operators. This is particularly important because most travelers to St. Barts transit through Sint Maarten (SXM) or Puerto Rico (SJU), where international documentation is checked multiple times. In 2026, even infants and children must have their own individual passports to clear customs. Attempting to enter with only a driver’s license or a birth certificate will result in a denied boarding at your point of departure, as there are no "closed-loop" cruise exceptions for air arrivals in this territory.