The Circuit Court of Cook County is the largest of the 24 circuit courts in the judiciary of Illinois as well as one of the largest unified court systems in the United States – second only in size to the Superior Court of Los Angeles County since that court merged with other courts in 1998.

The judiciary of Illinois is the unified court system of Illinois primarily responsible for applying the Constitution and law of Illinois. It consists of the Supreme Court, the Appellate Court, and circuit courts. The Supreme Court oversees the administration of the court system.