The Cook County State's Attorney functions as the state of Illinois's district attorney for Cook County, Illinois, and heads the second-largest prosecutor's office in the United States. The office has over 700 attorneys and 1,100 employees. In addition to direct criminal prosecution, the state's attorney's office files legal actions to enforce child support orders, protect consumers and the elderly from exploitation, and assist thousands of victims of domestic violence every year.

Cook County is the most populous county in the U.S. state of Illinois and the second-most-populous county in the United States, after Los Angeles County, California. More than 40 percent of all residents of Illinois live within Cook County. As of 2020, the population was 5,275,541. The county seat is Chicago, the most populous city in Illinois and the third most populous city in the United States. The county is at the center of the Chicago metropolitan area.