- Nation: Union
- Type: Ironclad (Passiac Class Monitor)
- Displacement: 1,875 tons
- Crew: 75
- Wartime Service Dates: 1863-1865
- Civil War Armament: 1 x 15-inch Dahlgren, 1 x 11-inch Dahlgren
- Notes: With the success of USS Monitor, the US Navy sought to produce more ships of a similar design. Improving on the original, the monitors of the Passiac-class included enhanced features such as an armored pilot house. Commissioned in February 1863, USS Nantucket, was sent to Charleston where it participated in attacks against the harbor forts. Despite the improvements in design, Nantucket and the other Passiac-class monitors were poor sea boats and prone to the same type of swamping that sank USS Monitor. As a result, the Navy limited their operations to coastal waters.