John Henry Eaton was an American politician and ambassador from Tennessee who served as U.S. Senator and as U.S. Secretary of War in the administration of Andrew Jackson. He was 28 years, 4 months, and 29 days old when he entered the Senate, making him the youngest U.S. Senator in history.

The United States Senate is the upper chamber of the United States Congress. The United States Senate and the lower chamber of Congress, the United States House of Representatives, comprise the federal bicameral legislature of the United States. Together, the Senate and the House maintain authority under Article One of the U.S. Constitution to pass or defeat federal legislation. The Senate has exclusive power to confirm U.S. presidential appointments, approve or reject treaties, and try cases of impeachment brought by the House. The Senate and the House provide a check and balance on the powers of the executive and judicial branches of government.