The Illinois Department of Natural Resources (IDNR) is the code department   of the Illinois state government that operates the state parks and state recreation areas, enforces the fishing and game laws of Illinois, regulates Illinois coal mines, operates the Illinois State Museum system, and oversees scientific research into the soil, water, and mineral resources of the state. In 2017, the Illinois Historic Preservation Division was added to its portfolio. It is headquartered in the state capital of Springfield.
The former Illinois Department of Conservation was reorganized into the Illinois Department of Natural Resources by executive order in 1995. The reorganization, codified into state law by Public Act 89-50, also added functions of the former Illinois Department of Energy and Natural Resources and the Illinois Department of Mines and Minerals to the agglomerated agency 
As of 2009, the Illinois Department of Natural Resources was divided up into 16 offices and bureaus 
- Architecture, Engineering and Grants
- Compliance, Equal Employment Opportunity and Ethics
- Law Enforcement
- Land Management
- Legal Counsel
- Mines & Minerals
- Public Events, Programs & Promotions
- Public Services and Education
- Realty & Environmental Planning
- Resource Conservation
- State Museums
- Water Resources
- State Surveys
In 2017, parts of the Illinois Historic Preservation Agency, were folded in the IDNR and became the Illinois Historic Preservation Division.
As of fiscal year 2006, the Illinois Department of Natural Resources had a budget of $187.1 million  Its headquarters is located at 1 Natural Resources Way, Springfield, Illinois 62702, adjacent to the Illinois State Fairgrounds 
- Uphoff, Judy Lee (2012). "The Governor and the Executive Branch". In Lind, Nancy S.; Rankin, Erik. Governing Illinois: Your Connection to State and Local Government (PDF) (4th ed.). Center Publications, Center for State Policy and Leadership, University of Illinois at Springfield. pp. 78–79. ISBN 978-0-938943-28-0.
- 20 ILCS 5/5-15
- 20 ILCS 801/1-5 (Illinois Compiled Statutes).
- Illinois DNR.
- Illinois Blue Book: 2005-2006, page 249.
- Illinois DNR.