Vermilion County is a county in the eastern part of the U.S. state of Illinois, between the Indiana border and Champaign County. It was established in 1826 and was the 45th of Illinois' 102 counties. According to the 2020 United States census, it had a population of 74,188. It contains 21 incorporated settlements; the county seat and largest city is Danville.

Danville is a city in and the county seat of Vermilion County, Illinois, United States. As of the 2020 census, its population was 29,204. It is the principal city of the Danville metropolitan area.