Stephen Decatur Jr. (; January 5, 1779 March 22, 1820) was an American naval officer and commodore. He was born on the eastern shore of Maryland in Worcester County. His father, Stephen Decatur Sr., was a commodore in the United States Navy who served during the American Revolution; he brought the younger Stephen into the world of ships and sailing early on. Shortly after attending college, Decatur followed in his father's footsteps and joined the U.S. Navy at the age of nineteen as a midshipman.Decatur supervised the construction of several U.S. naval vessels, one of which he later commanded. Promoted at age 25, he is the youngest man to reach the rank of captain in the history of the United States Navy. He served under three presidents, and played a major role in the early development of the U.S. Navy. In almost every theater of operation, Decatur's service was characterized by acts of heroism and exceptional performance. His service in the U.S. Navy took him through both Barbary Wars in North Africa, the Quasi-War with France, and the War of 1812 with Britain. He was renowned for his natural ability to lead and for his genuine concern for the seamen under his command. His numerous naval victories against Britain, France and the Barbary states established the United States Navy as a rising power.

During this period he served aboard and commanded many naval vessels and ultimately became a member of the Board of Navy Commissioners. He built a large home in Washington, known as Decatur House, on Lafayette Square, and was the center of Washington society in the early 19th century. He became an affluent member of Washington society and counted James Monroe and other Washington dignitaries among his personal friends.Decatur's career came to an early end when he was killed in a duel with Commodore James Barron. They fought after he refused to retract remarks he had made about Barron's conduct in the ChesapeakeLeopard affair in 1807. Decatur emerged as a national hero in his own lifetime, becoming the first post-Revolutionary War hero. His name and legacy, like that of John Paul Jones, became identified with the United States Navy.

The First Barbary War (1801–1805), also known as the Tripolitan War and the Barbary Coast War, was the first of two Barbary Wars, in which the United States and Sweden fought against the four North African states known collectively as the "Barbary States".The cause of the U.S. participation was pirates from the Barbary States seizing American merchant ships and holding the crews for ransom, demanding the U.S. pay tribute to the Barbary rulers. United States President Thomas Jefferson refused to pay this tribute. Sweden had been at war with the Tripolitans since 1800.