USS Constitution, also known as Old Ironsides, is a three-masted wooden-hulled heavy frigate of the United States Navy. She is the world's oldest commissioned naval warship still afloat. She was launched in 1797, one of six original frigates authorized for construction by the Naval Act of 1794 and the third constructed. The name "Constitution" was among ten names submitted to President George Washington by Secretary of War Timothy Pickering in March of 1795 for the frigates that were to be constructed. Joshua Humphreys designed the frigates to be the young Navy's capital ships, and so Constitution and her sister ships were larger and more heavily armed and built than standard frigates of the period. She was built at Edmund Hartt's shipyard in the North End of Boston, Massachusetts. Her first duties were to provide protection for American merchant shipping during the Quasi-War with France and to defeat the Barbary pirates in the First Barbary War.

A frigate is a type of warship. In different eras, the roles and capabilities of ships classified as frigates have varied.