Bull Valley is a village in McHenry County, Illinois, United States. The population was 1,128 at the 2020 census. Surrounded by larger, exurb towns of Crystal Lake, Woodstock, and McHenry, the village prides itself in its rural, low-density character. The village is in the outer most ring of the Chicago suburbs.

McHenry County is a county located in the U.S. state of Illinois. According to the 2020 Census, it had a population of 310,229, making it the sixth-most populous county in Illinois. Its county seat is Woodstock. McHenry County is one of the five Illinois collar counties in the Chicago-Naperville-Elgin, IL-IN-WI Metropolitan Statistical Area. Long known as a center of recreation along with agriculture in the western portion, it has more recently experienced rapid rates of suburbanization, exurbanization and urbanization, but the western portions of the county remain primarily agricultural and rural.