Montgomery County is located in the southwestern portion of the U.S. state of Ohio. As of the 2020 census, the population was 537,309, making it the fifth-most populous county in Ohio. The county seat is Dayton. The county was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada. Montgomery County is part of the Dayton, Ohio Metropolitan Statistical Area.
