The Illinois Department of Corrections (IDOC) is the code department of the Illinois state government that operates the adult state prison system. The IDOC is led by a director appointed by the Governor of Illinois, and its headquarters are in Springfield.

The Government of Illinois, under Illinois' Constitution, has three branches of government: Executive, Legislative, and Judicial. The State's executive branch is split into several statewide elected offices, with the Governor as chief executive and head of state, and has numerous departments, agencies, boards and commissions. Legislative functions are granted to the General Assembly, a bicameral body consisting of the 118-member House of Representatives and the 59-member Senate. The judiciary is composed of the Supreme Court of Illinois and lower courts.