The Charleston Harbor is an inlet of the Atlantic Ocean at Charleston, South Carolina. The inlet is formed by the junction of Ashley and Cooper rivers at 32°49′7.10″N 79°55′40.41″W. Morris and Sullivan's Islands shelter the entrance. Charleston Harbor forms part of the Intracoastal Waterway.
Like most river mouths in the Southeast of the United States, the inlet is part of a drowned coastline, defined by a rise in sea level in recent geologic time.