Jerome County is a county in the U.S. state of Idaho. As of the 2020 Census the county had a population of 24,237. The county seat and largest city is Jerome. The county was created by the Idaho Legislature on February 8, 1919, by a partition of Lincoln County. It was named after either Jerome Hill, a developer of the North Side Irrigation Project, his son-in-law Jerome Kuhn, or his grandson Jerome Kuhn, Jr.

Jerome is a city in and county seat of Jerome County, Idaho, United States. The population was 10,890 at the 2010 census, up from 7,780 in 2000. The city is the county seat of Jerome County, and is part of the Twin Falls Micropolitan Statistical Area. It is the second largest city in Idaho's Magic Valley region, second only to Twin Falls which is located 10 miles (16 km) southeast. Jerome's economy is largely agrarian, with dairy farming being one of the main revenue sources for the local economy.