The U.S. has agreements with over 100 countries (the " Six-Month Club ") that waive this requirement. For citizens of these countries, a passport only needs to be valid for the duration of their intended stay.
Many countries require your passport to be valid for at least . If your passport expires sooner than this window, you may be denied boarding by your airline or entry by border officials. 6 Month Rule
For U.S. Lawful Permanent Residents (Green Card holders), the "6 month rule" refers to travel outside the United States. like the Schengen Area
Some regions, like the Schengen Area , generally require only three months of validity beyond your planned departure date. Permanent Residency (Immigration) 6 Month Rule