USS Dunderberg, which is a Swedish word meaning "thunder(ing) mountain," was an ocean-going casemate ironclad of 14 guns. She resembled an enlarged, two-masted version of the Confederate casemate ironclad CSS Virginia. She was originally designed to have both gun turrets and a casemate but the turrets were deleted while the ship was still being built. Construction began in 1862, but progress was slow and she was not launched until after the end of the American Civil War in 1865.