Peoria is a city in and county seat of Peoria County, Illinois, United States. Located on the Illinois River, the city had a population of 113,150 as of the 2020 census. It is the principal city of the Peoria metropolitan area in Central Illinois, consisting of the counties of Fulton, Marshall, Peoria, Stark, Tazewell, and Woodford, which had a population of 402,391 in 2020.