Marengo is a town in and the county seat of Iowa County, Iowa, United States. It has served as the county seat since August 1845, even though it was not incorporated until July 1859. The population was 2,435 in the 2020 census, a decline from 2,535 in 2000.

Iowa County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 16,662. The county seat is Marengo.