Chillum is an unincorporated area and census-designated place in Prince George's County, Maryland, United States, bordering Washington, D.C., and Montgomery County. In addition to being its own unincorporated neighborhood, Chillum is also a census-designated place covering a larger area than the Chillum neighborhood. As of the 2010 census, the Chillum CDP included Chillum, as well as the adjacent unincorporated communities of Avondale, Carole Highlands, Green Meadows, and Lewisdale.