This is a list of law enforcement agencies in the state of Illinois.
According to the US Bureau of Justice Statistics' 2008 Census of State and Local Law Enforcement Agencies, the state had 877 law enforcement agencies employing 41,277 sworn police officers, about 321 for each 100,000 residents.
State agencies
- Illinois Attorney General's Office
- Department of Investigations
- Illinois Attorney General Police
- Illinois Commerce Commission Police
- Illinois Department of Corrections
- Illinois Department of Human Services Police Department
- Illinois Department of Mental Health Police
- Illinois Department of Natural Resources
- Illinois Conservation Police
- Illinois Department of Revenue Police
- Bureau of Criminal Investigations
- Illinois Gaming Board
- Illinois Secretary of State
- Illinois Secretary of State Capitol Police
- Illinois Secretary of State Police
- Illinois State Fire Marshal Arson Investigation
- Illinois State Police
County agencies
Sheriff's departments/offices
County Forest Preserve police departments
- Cook County Forest Preserve Police Department
- DuPage County Forest Preserve Police Department
- Kane County Forest Preserve Police Department
- Lake County Forest Preserve District - Operations and Public Safety Department
- Will County Forest Preserve Police Department
Other county departments
- Cook County Hospital Police Department
- McHenry County Conservation Police Department
- Oak Forest Hospital Department of Public Safety
- Vermilion County Conservation Police Department
Municipal agencies
Park District police agencies
Calumet Memorial Park Police Department
- Berwyn Park District Police Department
- Canton Park District Police Department
- Crystal Lake Park District Police Department
- Decatur Park District Police Department
- East St Louis Park District Police Department
- Fondulac Park District Police Department
- Fox Valley Park District Police Department
- Hawhorne Park District Police Department
- Kewanee Park District Police Department
- Lockport Township Park District Police Department
- Markham Park District Police Department
- Medinah Park District Police Department
- Morton Grove Park District Police Department
- Naperville Park District Police Department
- Pekin Park District Police Department
- Peoria Park District Police Department
- Quincy Park District Police Department
- Rockford Park District Police Department
- Round Lake Area Park District Police Department
- Springfield Park District Police Department
- Zion Park District Police Department
Special district agencies
- Abraham Lincoln Capital Airport Police Department
- Chicago Zoological Society Police Department
- Effingham Water Authority Police Department
- Metra Police Department
- Metropolitan Airport Authority of Rock Island County Public Safety
- Metropolitan Water Reclamation District of Greater Chicago Police Department
College and university agencies
Community or junior college agencies
