William Post Mansion, also known as the Post Mansion Inn, is a historic home located at Buckhannon, Upshur County, West Virginia. It was originally built in the 1860s and extensively renovated in 1891 in the Neo-Classical Revival style. It is a 2+1⁄2-story, brick dwelling with a three-story stone tower. The front facade features a portico with Doric order columns. A gymnasium was built over the porte cochere and a carport was added in the 1930s. Also on the property are a number of outbuildings related to a dairy, including a corn crib/granary, hay barn, one large equipment shed and two additional storage sheds The property also has a guest house and a rustic gazebo.