Big Otter Mill, also known as Forbes Mill, is a historic grist mill located near Bedford, Bedford County, Virginia, USA. It was built about 1920 and is a large, 2½-story, mortise-and-tenon framed mill building, topped by an unusual and picturesque mansard roof. The mill retains a nearly complete set of early-20th century machinery, including a 13-feet diameter water wheel, which was used until the late 1940s. Also on the property are a contributing mill race and the foundation of a store. The building is under restoration as a mill museum.