Great Mills is an unincorporated community in St. Mary's County, Maryland, United States. Great Mills High School serves the lower end of the county, including the town (census CDP) of Lexington Park.
The area is site of some of the oldest agricultural settlements in Maryland, as well as English speaking North America. It had many links to the original Maryland colony in St. Mary's City.
It is also now a suburb of Lexington Park and the Patuxent River Naval Air Station.
The area was part of the original agricultural expansion after the initial settling of the first Maryland Colony in St. Mary's City, which is located several miles south of Great Mills. Early planters established farms in the area by the mid to late 17th century.