Stephen Decatur, Jr. (January 5, 1779 - March 22, 1820) was an American naval officer notable for his heroism in actions at Tripoli, Libya and in the War of 1812.

He was born in Sinepuxent, Maryland, and was appointed midshipman in the Navy on April 30, 1798, serving in the USS United States.

As a lieutenant, in the war against Tripoli, on February 16, 1804, he went into the harbor, recaptured the USS Philadelphia, and then destroyed her.

On October 25, 1812, now commanding the United States, he captured the HMS Macedonian. In 1814 he flew a pennant as Commodore commanding the USS President and three smaller vessels in the West Indies. Unfortunately he fell in with the British West Indies Squadron January 15, 1815, and had to surrender the President after a fierce fight.

Between 1816 and 1820, Decatur was a Navy Commissioner.

In 1820, he feuded with Commodore James Barron; they fought a duel which resulted in Decatur's death.