Derby is a town in Orleans County, Vermont, United States. The population was 4,604 at the 2000 census. The town contains four unincorporated villages: Beebe Plain, Clyde Pond, Lake Salem and North Derby; and two incorporated villages: Derby Center and Derby Line.The Town of Derby encompasses the largest area in Orleans County. As of the 2010 censuses, Derby surpassed the city of Newport to also become the most-populous community in the county.