Hamilton is a city in Hancock County, Illinois, United States. The population was 2,951 at the 2010 census, a decline from 3,029 in 2000. The city is located directly across the Mississippi River from Keokuk, Iowa. Hamilton is the largest city in Hancock County.

Hancock County is a county in the U.S. state of Illinois. According to the 2020 census, it has a population of 17,620. Its county seat is Carthage, and its largest city is Hamilton. The county is composed of rural towns with many farmers.