Lake Monticello is a census-designated place (CDP) in Fluvanna County, Virginia, United States. The population was 9,920 at the 2010 census, an increase of over 44% from 2000. The community is centered on a lake of the same name, which is formed by a dam on a short tributary of the nearby Rivanna River. Lake Monticello is part of the Charlottesville Metropolitan Statistical Area. It's essentially a bedroom community of Charlottesville, and to a smaller extent Richmond.