Giles County is a county located in the U.S. state of Virginia on the West Virginia state line. As of the 2020 census, the population was 16,787. Its county seat is Pearisburg. Giles County is included in the Blacksburg-Christiansburg, VA Metropolitan Statistical Area. Giles County is the location of Mountain Lake, one of only two natural fresh water lakes in Virginia. The lake drains into Little Stony Creek, which passes over a waterfall known as The Cascades before reaching the New River.