In the United States, a natural-born citizen is one who is born on U.S. soil or to parents who are themselves U.S. citizens. U.S. citizens who gain their citizenship via a naturalization process are not considered natural-born citizens.
There has been significant disagreement over who is considered a natural-born citizen and what constitutes U.S. territory. U.S. soil includes U.S. military installations, but it does not include U.S. territories such as Guam or the Virgin Islands. It is also accepted that a child born to citizens of the United States, no matter where his place of birth, is a natural-born citizen.