Glassmanor is an unincorporated community and census-designated place in Prince George's County, Maryland, United States. As of the 2020 census, it had a population of 18,430. In the 1990 and 2000 censuses, the United States Census Bureau had placed Glassmanor and the adjacent community of Oxon Hill in the "Oxon Hill-Glassmanor" census-designated place for statistical purposes. Glassmanor was last delineated separately in 1980, when the CDP recorded a population of 7,751.