Greater Upper Marlboro is an area of Prince George's County, Maryland, United States, that completely surrounds Upper Marlboro, the county seat. It was formerly a census-designated place (CDP), with a population of 18,720 at the 2000 census. However, the 2010 census divided the area into several smaller CDPs, including portions of Marlboro Meadows, Brock Hall, Marlboro Village, Queenland, and Croom.