Southbury is a town in western New Haven County, Connecticut, USA. Southbury is north of Oxford and Newtown, and east of Brookfield. Its population was 19,904 at the 2010 census.Southbury comprises sprawling rural country areas, suburban neighborhoods, and historic districts. It is a short distance from major business and commercial centers, and is within 80 miles of New York City and 40 miles of Hartford; the latter the capital of Connecticut.Southbury is the only community in the country with the name "Southbury", which is why the town seal reads Unica Unaque, meaning "The One and Only.