Selbyville is a town in Sussex County, Delaware, United States. The population was 2,167 at the 2010 census, an increase of 31.7% over the previous decade. It is part of the Seaford, Delaware Micropolitan Statistical Area. Selbyville traces its history back to its founding in 1778. It was incorporated in 1902. Selbyville was originally known as Sandy Branch due to its location on a branch of that name emanating in the Cypress Swamp at the head of the St. Martin's River.