The report was made after a 21-year-old woman and an unknown man drove in a silver VW Golf to Apley Woods from shops on Bagley Drive in Wellington.
The car was parked near Severn Hospice off Apley Castle and the pair then made their way into the wooded area.
It is alleged the man sexually assaulted the woman while in the woods.
They left the area and returned to Bagley Drive in the car.
Police say it happened at about midday on June 14 and are encouraging witnesses, or anyone with information, to come forward.
Anyone who saw the VW Golf or the two individuals in the area are asked to contact DS Steve Goddard on 01952 214712, reference 443i of June 14.