The Fourteenth Amendment (Amendment XIV) to the United States Constitution was adopted on July 9, 1868, as one of the Reconstruction Amendments. Considered one of the most consequential amendments, it addresses citizenship rights and equal protection under the law at all levels of government. The Fourteenth Amendment was a response to issues affecting freed slaves following the American Civil War, and its enactment was bitterly contested. States of the defeated Confederacy were required to ratify it to regain representation in Congress. The amendment, particularly its first section, is one of the most litigated parts of the Constitution, forming the basis for landmark Supreme Court decisions, such as Brown v. Board of Education (1954; prohibiting racial segregation in public schools), Loving v. Virginia (1967; ending interracial marriage bans), Roe v. Wade (1973; recognizing federal right to abortion until overturned in 2022), Bush v. Gore (2000; settling 2000 presidential election), Obergefell v. Hodges (2015; extending right to marry to same-sex couples), and Students for Fair Admissions v. Harvard (2023; prohibiting affirmative action in most college admissions).

The amendment's first section includes the Citizenship Clause, Privileges or Immunities Clause, Due Process Clause, and Equal Protection Clause. The Citizenship Clause broadly defines citizenship, superseding the Supreme Court's decision in Dred Scott v. Sandford (1857), which held that Americans descended from African slaves could not become American citizens. The Privileges or Immunities Clause was interpreted in the Slaughter-House Cases (1873) as preventing states from impeding federal rights, such as the freedom of movement. The Due Process Clause builds on the Fifth Amendment to prohibit all levels of government from depriving people of life, liberty, or property without substantive and procedural due process. Additionally, the Due Process Clause supports the incorporation doctrine, by which portions of the Bill of Rights have been applied to the states. The Equal Protection Clause requires each state to provide equal protection under the law to all people, including non-citizens, within its jurisdiction.

The second section superseded the Three-fifths Compromise, apportioning the House of Representatives and Electoral College using each state's adult male population. In allowing states to abridge voting rights "for participation in rebellion, or other crime," this section approved felony disenfranchisement. The third section disqualifies federal and state candidates who "have engaged in insurrection or rebellion," but in Trump v. Anderson (2024), the Supreme Court left its application to Congress for federal elections and state governments for state elections. The fourth section affirms public debt authorized by Congress while declining to compensate slaveholders for emancipation. The fifth section provides congressional power of enforcement, but Congress' authority to regulate private conduct has shifted to the Commerce Clause, while the anti-commandeering doctrine restrains federal interference in state law.

Section 1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

Section 1 of the Fourteenth Amendment formally defines United States citizenship and protects various civil rights from being abridged or denied by any state law or state action. In Shelley v. Kraemer (1948), the Supreme Court held that the Fourteenth Amendment's historical context of countering the discriminatory Black Codes of southern states must be used in its interpretation. Primarily written by Representative John Bingham, Section 1 is the most frequently litigated part of the amendment, and this amendment is the most frequently litigated part of the Constitution.

The Citizenship Clause overruled the Supreme Court's Dred Scott decision that African Americans could not become citizens. The clause constitutionalized the Civil Rights Act of 1866's grant of citizenship to all born within the United States, except the children of foreign diplomats. Compared against European jus sanguinis laws that assign citizenship by one's parents, historians have framed the United States' Citizenship Clause as an extension of the Fourteenth Amendment's egalitarian principles.

Congress' debate over the Citizenship Clause shows explicit rejection of Senator Edgar Cowan's anti-Romani sentiment, affirming that birthright citizenship cannot be revoked from children born to disfavored ethnic minorities. Birthright citizenship was meant to repudiate the American Colonization Society's repatriation of freeborn people of color and emancipated slaves to Africa. In United States v. Wong Kim Ark (1898), the Supreme Court confirmed that children born in the United States receive birthright citizenship, regardless of whether their parents are non-citizen immigrants.

In Elk v. Wilkins (1884), the Supreme Court interpreted the Citizenship Clause as granting birthright citizenship to all born within the jurisdiction of the United States and allowing Congress to establish alternative pathways for naturalization. Consistent with the views of the clause's author, Senator Jacob M. Howard, the Supreme Court held that because Indian reservations are not under the federal government's jurisdiction, Native Americans born on such land are not entitled to birthright citizenship. The 1887 Dawes Act offered citizenship to Native Americans who accepted private property as part of cultural assimilation, while the 1924 Indian Citizenship Act offered citizenship to all Native Americans born within the nation's territorial limits.