The first inauguration of James Madison as the fourth president of the United States was held on Saturday, March 4, 1809, in the chamber of the House of Representatives at the United States Capitol in Washington, D.C. The inauguration marked the commencement of the first four-year term of James Madison as president and the second term of George Clinton as vice president. The presidential oath was administered by Chief Justice John Marshall. The President wore a 100% American-made wool suit, and the first official inaugural ball occurred at Long's Hotel, with ticket prices being $4. Clinton died 3 years, 47 days into this term, and the office remained vacant for the balance of it. Clinton was the first vice president to die in office.

The oath of office of the president of the United States is the oath or affirmation that the president of the United States takes upon assuming office. The wording of the oath is specified in Article II, Section One, Clause 8, of the United States Constitution, and a new president must take it before exercising or carrying out any official powers or duties.