United States citizenship can be acquired by birthright in two situations: by virtue of the person's birth within United States territory while under the jurisdiction thereof (jus soli) or because at least one of their parents was a U.S. citizen at the time of the person's birth (jus sanguinis). Birthright citizenship contrasts with citizenship acquired in other ways, for example by naturalization.
Birthright citizenship is explicitly guaranteed to anyone born under the legal "jurisdiction" of the U.S. federal government by the Citizenship Clause of the Fourteenth Amendment to the United States Constitution (adopted July 9, 1868), which states: