Blenheim is a town in Marlboro County, South Carolina, United States. The population was 154 at the 2010 census. It is named for Blenheim Palace in Oxfordshire, England. Blenheim Palace was the residence of the Duke of Marlborough, after whom Marlboro County is named. Blenheim Ginger Ale was originally bottled in Blenheim, with the local mineral water.