North Chicago is a city in Lake County, Illinois, United States, and a suburb of the Chicago metropolitan area. The population was 30,759 at the 2020 census making it the third-most populous city by population in the county, after Waukegan and Mundelein.

Lake County is situated in the northeastern corner of the U.S. state of Illinois, along the shores of Lake Michigan. As of the 2020 census, it has a population of 714,342, making it the third-most populous county in Illinois. Its county seat is Waukegan, the tenth-largest city in Illinois. The county is primarily suburban, with some urban areas and some rural areas. Due to its location, immediately north of Cook County, Lake County is one of the collar counties of the Chicago metropolitan area. Its northern boundary is the Wisconsin state line.