Authorities said it happened late Wednesday night in a parking lot at Duke Manor Apartments on South LaSalle Street.
A woman told police that a man wearing a hoodie approached her while she was taking out the trash. She said the man sexually assaulted her and then fled.
There is no further description of the suspect at this time.
Anyone with information is asked to call Investigator Mussatti at (919) 560-4440, ext. 29330 or CrimeStoppers at (919) 683-1200.