The Fourteenth Amendment to the United States Constitution (Amendment XIV) is one of the post-Civil War amendments (known as the Reconstruction Amendments), first intended to secure rights for former slaves. It includes the Due Process and Equal Protection Clauses among others. It was proposed on June 13, 1866, and ratified on July 9, 1868. It is perhaps the most significant structural change to the Constitution since the passage of the United States Bill of Rights. The amendment provides a broad definition of United States citizenship, overturning the Dred Scott case, which excluded African Americans. It requires the states to provide equal protection under the law to all persons (not only to citizens) within their jurisdictions, and was used in the mid-20th century to dismantle legal segregation, as in Brown v. Board of Education. Its Due Process Clause has driven much important and controversial case law regarding privacy rights, abortion (see Roe v. Wade), and other issues.

The other two post-Civil War amendments are the Thirteenth Amendment (banning slavery) and the Fifteenth Amendment (banning race-based voting qualifications). According to Supreme Court Justice Noah Swayne, "Fairly construed, these amendments may be said to rise to the dignity of a new Magna Carta."