Hardin County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 16,878. The county seat is Eldora. The county was named in honor of Col. John J. Hardin, of Illinois, who was killed in the Mexican–American War.

Eldora is a city and the county seat of Hardin County, Iowa, United States. The population was 2,663 at the time of the 2020 census. It is the county seat of Hardin County.