Fremont County is a county located in the U.S. state of Iowa. As of the 2020 census the population was 6,605, making it the state's seventh-least populous county. The county seat is Sidney. The county was formed in 1847 and named for the military officer John C. Frémont.

Sidney is a city in Fremont County, Iowa, United States. The population was 1,070 at the time of the 2020 census. It is the county seat of Fremont County and is one of the smallest county seats in the state.