Operation Greylord was an investigation conducted jointly by the Federal Bureau of Investigation (FBI), the IRS Criminal Investigation Division, the U.S. Postal Inspection Service, the Chicago Police Department Internal Affairs Division and the Illinois State Police into corruption in the judiciary of Cook County, Illinois. The FBI named the investigation "Operation Greylord" after a racehorse, after other suggested names were rejected by FBI Headquarters as being too close to the subject matter of the investigation, should they become known.