Clarksville is an unincorporated community in Howard County, Maryland; the second highest-earning county in the United States according to the U.S. Census Bureau. The community is named for William Clark, a farmer who owned much of the land on which the community now lies and served as a postal stop that opened on the 4th of July 1851.

Howard County is located in the U.S. state of Maryland. As of the 2020 census, the population was 334,529. Since there are no incorporated municipalities, there is no incorporated county seat either. Therefore, its county seat is the unincorporated community of Ellicott City. Howard County is included in the Baltimore-Columbia-Towson, MD Metropolitan Statistical Area, which is part of the larger Washington–Baltimore combined statistical area.