St. Charles or Saint Charles is a city in Kane and DuPage Counties, Illinois, United States. The population was 33,081 at the 2020 census, and was estimated at 33,482 in 2024. It lies roughly 35 miles west of Chicago on Illinois Route 64. The official city slogan is "Pride of the Fox", after the Fox River that runs through the center of town. St. Charles is part of a tri-city area along with Geneva and Batavia, all western Chicago suburbs of similar size and socioeconomic condition.