Pike County is a county in the U.S. state of Illinois. It is located between the Mississippi River and the Illinois River in western Illinois. According to the 2020 United States Census, it had a population of 14,739. Its county seat is Pittsfield.

Pittsfield is a city in and the county seat of Pike County, Illinois, United States. The population was 4,576 at the 2010 census, an increase from 4,211 in 2000.