Oliver Wendell Holmes Jr., American colonel, lawyer, and jurist, Associate Justice of the Supreme Court of the United States (born 1841)

Oliver Wendell Holmes Jr. was an American jurist who served as an associate justice of the U.S. Supreme Court from 1902 to 1932. Holmes is one of the most widely cited and influential Supreme Court justices in American history, noted for his long tenure on the Court and for his pithy opinions – particularly those on civil liberties and American constitutional democracy – and deference to the decisions of elected legislatures. Holmes retired from the Court at the age of 90, an unbeaten record for oldest justice on the Supreme Court. He previously served the Union as a brevet colonel in the American Civil War, as an associate justice and chief justice of the Massachusetts Supreme Judicial Court, and as Weld Professor of Law at his alma mater, Harvard Law School. His positions, distinctive personality, and writing style made him a popular figure, especially with American progressives.

An associate justice of the Supreme Court of the United States is a justice of the Supreme Court of the United States, other than the chief justice of the United States. The number of associate justices is eight, as set by the Judiciary Act of 1869.

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.