John Marshall Harlan II, American lawyer and jurist, Associate Justice of the US Supreme Court (died 1971)

John Marshall Harlan was an American lawyer and jurist who served as an associate justice of the U.S. Supreme Court from 1955 to 1971. Harlan is usually called John Marshall Harlan II to distinguish him from his grandfather, John Marshall Harlan, who served on the U.S. Supreme Court from 1877 to 1911.

An associate justice or associate judge is a judge of a court other than the chief justice in some jurisdictions. The title "Associate Justice" is used for members of the Supreme Court of the United States and some state supreme courts, and for some other courts in Commonwealth of Nations countries, as well as for members of the Supreme Court of the Federated States of Micronesia, a former United States Trust Territory. In other common law jurisdictions, the equivalent position is called "Puisne Justice".

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that turn on questions of U.S. constitutional or federal law. It also has 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." In 1803, the court asserted itself the power of judicial review, the ability to invalidate a statute for violating a provision of the Constitution via the landmark case Marbury v. Madison. It is also able to strike down presidential directives for violating either the Constitution or statutory law.