U.S. citizens with a valid U.S. tourist passport are not required to obtain a visa to enter the Schengen area. U.S. citizens may remain in the Schengen area, either for business or leisure, for a maximum of 3 months without a visa, according to the U.S. Department of State. U.S. citizens without a valid U.S. tourist passport are advised by the Department of State to contact the U.S. embassy in their destination country to apply for a visa.
U.S. citizens wishing to remain within the Schengen area for longer than 3 months during any 6 month period are required to apply for a visa from the Consulate of the first destination country within the Schengen area. Visa applications must be made at least 15 days and no earlier than 3 months in advance of the trip.
It is important to ensure that passports are stamped by immigration officials whenever entering and exiting the Schengen area. It is not necessary to pass through immigration controls when crossing borders between countries within the Schengen area.
The Schengen area comprises all member countries of the European Union, except for Bulgaria, Croatia, Cyprus, Ireland, Romania and the United Kingdom. Iceland, Norway, Switzerland and Liechtenstein, although not members of the European Union, are also included in the Schengen area.