Jasper County is a county located in the U.S. state of Illinois. According to the 2020 census, it has a population of 9,287. Its county seat is Newton.

Newton is a city in and the county seat of Jasper County, Illinois, United States. The population was 2,849 at the 2010 census, down from 3,069 at the 2000 census. Newton is home to a large coal-fired power plant operated by Illinois Power Generating Co and is close to Newton Lake State Fish and Wildlife Area and Sam Parr State Fish and Wildlife Area.