St. Marys is a city in Camden County, Georgia, United States, located on the southern border of Camden County on the St. Marys River in the state's Low Country. The Florida border is just to the south across the river, Cumberland Island National Seashore is to the northeast, and Kingsland, Georgia, is to the west. Jacksonville, Florida, is 38 miles south, and Savannah, Georgia, is 110 miles north.

Camden County is a county located in the southeastern corner of the U.S. state of Georgia. According to the 2020 census, its population was 54,768. Its county seat is Woodbine, and the largest city is Kingsland. It is one of the original counties of Georgia, created February 5, 1777. It is the 11th-largest county in the state of Georgia by area, and the 41st-largest by population.