USS Colossus (1864) was a steamer acquired by the Union Navy towards the end of the American Civil War. She was used to patrol navigable waterways of the Confederacy to prevent the South from trading with other countries. Colossus, a stern wheel steamer, was built in 1864 at Freedom, Pennsylvania; purchased 6 December 1864 at Cincinnati, Ohio, by the U.S. Navy; outfitted at Mound City, Illinois; and commissioned 24 February 1865, Acting Master F. G. Sampson in command.