Police said there has been three incidents in which a man has exposed himself to women visiting Endcliffe Park, just off Rustlings Road, in recent weeks.
The first happened at about 2.20pm on Wednesday, August 16, and then again just before 2.30pm. On both occasions the women targeted had been walking through the park.
Days later on Saturday, another woman came forward to say a man had exposed himself at 10.50am on Saturday, August 19.
Detectives have now released a e-fit picture of the man they are tracing in connection with the incidents.
A South Yorkshire Police spokeswoman said: "Officers believe it is the same man involved in all three incidents.
"If you know who he is, or recognise him, please call 101 or Crimestoppers anonymously on 0800 555111, quoting incident number 620 of 16 August 2017."