St. Charles is a planned community located in Charles County, Maryland, in the United States. It is situated approximately 22 miles south-southeast of Washington, D.C., and 24 miles from northern Virginia.
The community is positioned immediately south of Waldorf, which serves as its mailing address. In the 2000 census, St. Charles was delineated as a census-designated place (CDP) with a population of 33,379. By the 2010 census, it was included within the broader Waldorf CDP.