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.

The governor of Illinois is the head of government of Illinois, and the various agencies and departments over which the officer has jurisdiction, as prescribed in the state constitution. It is a directly elected position, votes being cast by popular suffrage of residents of the state. The governor is responsible for enacting laws passed by the Illinois General Assembly. Illinois is one of 13 states that does not have a gubernatorial term-limit along with Connecticut, Idaho, Iowa, Massachusetts, Minnesota, New York, Texas, Utah, Washington, Wisconsin, District of Columbia, Vermont, New Hampshire and Puerto Rico. The governor is commander-in-chief of the state's land, air and sea forces when they are in state service.