The Judiciary Act of 1789 was a United States federal statute enacted on September 24, 1789, during the first session of the First United States Congress. It established the federal judiciary of the United States. Article III, Section 1 of the Constitution prescribed that the "judicial power of the United States, shall be vested in one Supreme Court, and such inferior Courts" as Congress saw fit to establish. It made no provision for the composition or procedures of any of the courts, leaving this to Congress to decide.

The 1st United States Congress, comprising the United States Senate and the United States House of Representatives, met from March 4, 1789, to March 4, 1791, during the first two years of George Washington's presidency, first at Federal Hall in New York City and later at Congress Hall in Philadelphia. With the initial meeting of the First Congress, the United States federal government officially began operations under the new frame of government established by the 1787 Constitution. The apportionment of seats in the House of Representatives was based on the provisions of Article I, Section 2, Clause 3, of the Constitution. Both chambers had a Pro-Administration majority. Twelve articles of amendment to the Constitution were passed by this Congress and sent to the states for ratification; the ten ratified as additions to the Constitution on December 15, 1791, are collectively known as the Bill of Rights, with an additional amendment ratified more than two centuries later to become the Twenty-seventh Amendment to the United States Constitution.