Brantley County is a county located in the southeastern part of the U.S. state of Georgia. As of the 2020 census, the population was 18,021. The county seat is Nahunta. Brantley County is part of the Brunswick, Georgia metropolitan statistical area.

The Brunswick metropolitan area is the Coastal Georgian metropolitan statistical area centered on the principal city of Brunswick, Georgia. The U.S. Office of Management and Budget, Census Bureau and other entities define Brunswick's metropolitan statistical area as comprising Glynn, Brantley, and McIntosh counties, including the cities of Brunswick and Darien. According to the 2020 census, the metropolitan area had a population of 113,495.