It is reported that a woman in her 30s was raped by an unknown man on Staniforth Road in Darnall at sometime between 1.30pm on Saturday 13 August and 12.20am the following morning.
Police are now providing support to the woman.
A spokeswoman for South Yorkshire Police said: “An investigation into the circumstances surrounding the incident is under way, with officers reviewing CCTV footage of the area.
“Detectives are also working with the woman to establish the exact location of the incident and she continues to receive support from specialist officers.”
Anyone with information that may assist the investigation or who was in the area at the time is asked to call South Yorkshire Police on 101.