Howard County is located in the U.S. state of Maryland. As of the 2020 census, the population is 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 part of the Baltimore metropolitan area.

The county is home to Columbia, a planned community between Baltimore and Washington, D.C. with a population of approximately 100,000, founded in 1967.