The USS Housatonic was an American steam sloop that served in the Union Navy during the American Civil War. On February 17, 1864, the Housatonic was sunk in Charleston Harbor, South Carolina by the Confederate submarine H.L. Hunley, marking the first time in naval warfare that a submarine successfully sank an enemy warship. The sinking of the Housatonic represented a significant technological advancement that foreshadowed the future importance of submarines in naval combat.