For all visitors, formalities in Saint Barths require a valid passport. And, depending on the country of origin, a French visa valid for France except CTOM or DFA (French departments of America) with the mention COLLECTIVITE TERRITORIALE DE SAINT BARTHELEMY ET SAINT MARTIN must be issued by the French Embassy before departure.
For American and Canadian citizens, you must have a valid passport, obligatorily accompanied by a return or continuation of travel ticket, it is not necessary to have a visa if the stay is shorter or equal to 30 days. On the other hand, the passport must imperatively have a period of validity greater than 3 months at the time of entry into our territory.