In Asia, nations like China, Vietnam, Malaysia and Thailand enforce this rule. South American countries like Brazil, Venezuela and Bolivia also need a passport that's good for six months.
Many European countries (the Schengen states) require that your passport be valid for at least three months beyond your planned date of departure from the Schengen area.
Yes, you will be denied entry abroad if your passport is about to expire. Additionally, if you need a visa, you won't receive one with a valid passport of less than six (sometimes three) months. For this reason, you have to make sure that your passport is up-to-date before you travel.
Entry, Exit and Visa RequirementsYour passport must be valid for at least three months beyond the period of stay. Review our U.S. Travelers in Europe page. You will need proof of sufficient funds and a return plane ticket. For additional information about visas for the Schengen area, see the Schengen Visa page.
For entry into Greece, your passport should have at least six months of remaining validity. While Greek law requires three months of passport validity beyond the intended date of your departure, if you are transiting a country that requires six months of validity, you may not be permitted to continue your trip.
U.S. nationals, including U.S. dual nationals, must use a U.S. passport to enter and leave the United States. U.S. dual nationals may also be required by the country of their foreign nationality to use that country's passport to enter and leave that country.
Many European countries (the Schengen states) require that your passport be valid for at least three months beyond your planned date of departure from the Schengen area.