USS Constitution vs HMS Guerriere was a battle between an American and British ship during the War of 1812, about 400 miles (640 km) southeast of Halifax, Nova Scotia. It took place on the 19th of August 1812, one month after the war's first engagement between British and American forces. Guerriere was proceeding to Halifax for a refit, having been detached from a squadron which had earlier failed to capture Constitution. When the two ships encountered each other on August 19th, Guerriere's Captain James Richard Dacres engaged, confident of victory despite facing a bigger, stronger-manned, and better-armed U.S. ship. However, in the exchange of broadsides, Guerriere's masts were felled, and the ship reduced to a sinking condition. Constitution's crew took the British sailors on board and set Guerriere on fire, then returned to Boston with news of the victory, which proved to be important for American morale.

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.