General Requirements:
Portugal is a party to the Schengen agreement. As such, U.S. citizens may enter Portugal for up to 90 days for tourist or business purposes without a visa. The passport should be valid for at least three months beyond the period of stay.
Portuguese law requires some non-European Union foreign nationals to register with immigration officials within three working days of entering Portugal. The law affects those who transit another Schengen area country by air en route to Portugal and stay at noncommercial accommodations.
If an American citizen would like to ensure that his or her entry is properly documented, it may be necessary to request a stamp at an official point of entry, or download a “declaracão de entrada” from the Portuguese Immigration Service’s website, and submit it to a local SEF office or police station within 3 days of entry. Travelers without a stamp in their passport may be questioned about or asked to document the length of their stay in Schengen countries. If unable to do so, they could face possible fines.
General Consulates of Portugal: