DuPage County (/duːˈpeɪdʒ/ doo-PAYJ) is a county in the U.S. state of Illinois, and one of the collar counties of the Chicago metropolitan area. As of the 2020 census, the population was 932,877, making it Illinois’ second-most populous county. Its county seat is Wheaton.

Known for its vast tallgrass prairies, DuPage County has become mostly developed and suburbanized, although some pockets of farmland remain in the county’s western and northern parts. Located in the Rust Belt, the area is one of few in the region whose economy quickly became dependent on the headquarters of several large corporations due to its close proximity to Chicago. As steel mills closed in the 1970s and 1980s, several acres that were formerly industrialized areas were converted into business parks to meet the growing tax base. The county has a mixed socioeconomic profile and residents of Hinsdale, Naperville and Oak Brook include some of the wealthiest people in the Midwest. However, other cities in the county such as Aurora and Downers Grove have faced issues regarding local small business growth, affordable housing and elevating crime rates. On the whole, the county enjoys above average median household income levels and low overall poverty levels when compared to the national average. In 2018, Niche ranked two DuPage municipalities (Clarendon Hills at #22 and Naperville at #128) amongst the best places to live in America.