Clinton County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 42,018. Its county seat and largest city is Wilmington. The county is named for former U.S. Vice President George Clinton. Clinton County comprises the Wilmington, Ohio Micropolitan Statistical Area, which is also included in the Cincinnati-Wilmington-Maysville, OH-KY-IN Combined Statistical Area.