Lemont is a village located in Cook, DuPage, and Will counties in the U.S. state of Illinois, and is a south-west suburb of Chicago. The population was 17,629 as of the 2020 census. The village is situated on a hillside along the south banks of the Des Plaines River. It overlooks Waterfall Glen's Midwestern Bluff Savanna on the opposite side. Lemont is home to Argonne National Laboratory and other heavy industrial sites, and has a substantial European immigrant population.