If I'm understanding your question correctly, then it is the governor, which is currently Pat Quinn.
The Chief Executive Officer of the state of Illinois is the governor. In 2014, the governor of Illinois was Pat Quinn. He took the office in 2009.
The Governor of the State of Illinois.
Pat Quinn
Governor
Yes, the governor is considered the chief executive of Illinois.
While others have individual responsibilities the head of the Executive branch of the State Government is the State Governor, it can be said that that position acts as and is the Chief Administrator of the State of Illinois.
The Governor is the chief executive of each of the US states
In 1818, Shadrach Bond was elected Governor of Illinois, becoming the new state's first chief executive.
The chief state executive is the governor of the state.
CEO
The Governor of Illinois is the chief executive of the Illinois state government. Bruce Rauner is the 42nd and current Governor of Illinois. He was elected in 2014 and assumed office on January 12, 2015. He is a member of the Republican Party. The Governor in Illinois serves a four-year term and there is no limit on the number of terms a governor may serve.
The Chief Fiscal Control Officer of the Executive branch of the State of Illinois is the Comptroller. He or she is elected to terms of four years. The Comptroller reviews the bills and pays them, and participates in setting financial policies.