Dred Scott v. Sandford, 60 U.S. (19 How.) 393 (1857), was a landmark decision of the United States Supreme Court in which the Court held that the United States Constitution was not meant to include American citizenship for people of African descent, regardless of whether they were enslaved or free, and so the rights and privileges that the Constitution confers upon American citizens could not apply to them. The Supreme Court's decision has been widely denounced, both for how overtly racist the decision was and its crucial role in the start of the American Civil War four years later. Legal scholar Bernard Schwartz said that it "stands first in any list of the worst Supreme Court decisions". Chief Justice Charles Evans Hughes called it the Court's "greatest self-inflicted wound". Historian Junius P. Rodriguez said that it is "universally condemned as the U.S. Supreme Court's worst decision." Historian David Thomas Konig said that it was "unquestionably, our court's worst decision ever."The decision was made in the case of Dred Scott, an enslaved black man whose owners had taken him from Missouri, a slave-holding state, into Illinois and the Wisconsin Territory, where slavery was illegal. When his owners later brought him back to Missouri, Scott sued in court for his freedom and claimed that because he had been taken into "free" U.S. territory, he had automatically been freed and was legally no longer a slave. Scott sued first in Missouri state court, which ruled that he was still a slave under its law. He then sued in U.S. federal court, which ruled against him by deciding that it had to apply Missouri law to the case. He then appealed to the U.S. Supreme Court.

In March 1857, the Supreme Court issued a 72 decision against Scott. In an opinion written by Chief Justice Roger Taney, the Court ruled that people of African descent "are not included, and were not intended to be included, under the word 'citizens' in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States". Taney supported his ruling with an extended survey of American state and local laws from the time of the Constitution's drafting in 1787 that purported to show that a "perpetual and impassable barrier was intended to be erected between the white race and the one which they had reduced to slavery". Because the Court ruled that Scott was not an American citizen, he was also not a citizen of any state and, accordingly, could never establish the "diversity of citizenship" that Article III of the U.S. Constitution requires for a U.S. federal court to be able to exercise jurisdiction over a case. After ruling on those issues surrounding Scott, Taney continued further and struck down the entire Missouri Compromise as a limitation on slavery that exceeded the U.S. Congress's constitutional powers.

Although Taney and several other justices hoped the decision would permanently settle the slavery controversy, which was increasingly dividing the American public, the decision's effect was the opposite. Taney's majority opinion suited the slaveholding states, but was intensely decried in all the other states. The decision inflamed the national debate over slavery and deepened the divide that led ultimately to the American Civil War. In 1865, after the Union's victory, the Court's ruling in Dred Scott was superseded by the passage of the Thirteenth Amendment to the U.S. Constitution, which abolished slavery, and the Fourteenth Amendment, whose first section guaranteed citizenship for "all persons born or naturalized in the United States, and subject to the jurisdiction thereof".

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate and largely discretionary appellate jurisdiction over all federal and state court cases that involve a point of federal law, and original jurisdiction over a narrow range of cases, specifically "all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party." The Court holds the power of judicial review, the ability to invalidate a statute for violating a provision of the Constitution. It is also able to strike down presidential directives for violating either the Constitution or statutory law. However, it may act only within the context of a case in an area of law over which it has jurisdiction. The Court may decide cases having political overtones but has ruled that it does not have power to decide non-justiciable political questions.

Established by Article Three of the United States Constitution, the composition and procedures of the Supreme Court were initially established by the 1st Congress through the Judiciary Act of 1789. As later set by the Judiciary Act of 1869, the Court consists of the chief justice of the United States and eight associate justices. Each justice has lifetime tenure, meaning they remain on the Court until they die, retire, resign, or are removed from office. When a vacancy occurs, the president, with the advice and consent of the Senate, appoints a new justice. Each justice has a single vote in deciding the cases argued before the Court. When in majority, the chief justice decides who writes the opinion of the court; otherwise, the most senior justice in the majority assigns the task of writing the opinion.

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