The Dubois-Sarles Octagon is an octagon house located on South Street in Marlboro, New York, United States. It was listed on the National Register of Historic Places in 2002. First built around 1850 by the Dubois family, it was renovated in 1872 by the Sarleses. As a result it reflects two different architectural styles: Italianate and Second Empire. Unlike most other American octagon houses of the period, its interior follows a sidehall plan, rather than the radial center plan advocated by Orson Squire Fowler.