Seabrook Island, formerly known as Simmons Island, is a barrier island in Charleston County, South Carolina, United States. The population was 1,714 at the 2010 census, up from 1,250 in 2000.
Seabrook Island is part of the Charleston-North Charleston-Summerville metropolitan area.
Seabrook Island is located in southwestern Charleston County at 32°34′56″N 80°9′48″W (32.582173, -80.163332), bordered to the south by the Atlantic Ocean, to the west by the North Edisto River, and to the north by Bohicket Creek. The town extends to the east along the Atlantic shoreline as far as the Kiawah River, across which is the town of Kiawah Island. Most of the eastern border of the town, however, is next to unincorporated land. The city of Charleston is 25 miles (40 km) to the northeast.
According to the United States Census Bureau, the town of Seabrook Island has a total area of 7.0 square miles (18.1 km2), of which 6.0 square miles (15.5 km2) is land and 1.0 square mile (2.7 km2), or 14.74%, is water.
In 1666, British subject Lt. Col. Robert Sanford arrived on Seabrook as an explorer in royal service to King Charles II. By 1684, the local Stono Indians were persuaded to cede their lands to the proprietary government, which in turn sold the property to English settlers.