Dayton is a city located in Montgomery County, Ohio, in the United States. It serves as the county seat and is situated within the state's Miami Valley region. Geographically, it lies approximately 40 miles north of Cincinnati and 55 miles southwest of Columbus.
As of the 2020 United States census, Dayton had a population of 137,644, making it the sixth-most populous city in Ohio. The broader Dayton metropolitan area has an estimated population of 822,000 residents and ranks as the fourth-largest metropolitan area in the state.