Winfrey bought the unit in 2006 but never moved in.
Now, the Streeterville co-op is available to rent for $15,000 a month.
The master bedroom is more than 1,200 square feet.
The Chicago Tribune reports that Oprah once listed it for $6 million, but didn't sell it.
The co-op has three full baths, two fireplaces, a butler's pantry, a wine room and a custom kitchen.
Winfrey owns several other properties in the area. Her spokeswoman and listing agent declined to comment.
The Associated Press contributed to this report.