St. Simons Island is a barrier island and census-designated place located in the U.S. state of Georgia. It resides in St. Simons Island of Glynn County included in the Brunswick, Georgia Metropolitan Statistical Area. It has a total area of 17.7 square miles at 31°9′35″N 81°23′19″W. The elevation is 10 feet above sea level. As of the 2010 census data, it had a total population of 12,743. The population density was 799.4/sq mi. St. Simons Island is both a seaside resort and residential area.