The town of Bel Air is the county seat of Harford County, Maryland. According to the 2020 United States census, the population of the town was 10,661.The United States Census Bureau defines an urban area in northeast Maryland in which Bel Air is the principal settlement: the Bel Air–Aberdeen, MD urban area had a population of 214,647 as of the 2020 census, making it the 180th most-populous in the United States.