USS Marmora was a sternwheel steamer that served in the Union Navy during the American Civil War. Marmora was built in 1862 at Monongahela, Pennsylvania, as a civilian vessel, and was purchased for military service on September 17. Commissioned on October 21, the vessel served on the Yazoo River beginning the next month. She encountered Confederate naval mines on the Yazoo on December 11, and was present the next day when the ironclad USS Cairo was sunk by two mines. After further service on the Yazoo during the Battle of Chickasaw Bayou in late December, Marmora was assigned in January 1863 to a fleet that was preparing to operate against Confederate Fort Hindman, but was not present when the fort surrendered on January 11.