Fluvanna County is a county located in the Piedmont region of the Commonwealth of Virginia, United States. As of the 2020 census, the population was 27,249. Its county seat is Palmyra, while the most populous community is the census designated place of Lake Monticello. Fluvanna County is part of the Charlottesville, Virginia Metropolitan S…Fluvanna County is a county located in the Piedmont region of the Commonwealth of Virginia, United States. As of the 2020 census, the population was 27,249. Its county seat is Palmyra, while the most populous community is the census designated place of Lake Monticello. Fluvanna County is part of the Charlottesville, Virginia Metropolitan Statistical Area.