At around 3.15pm on Wednesday, April 24, it is reported that a 13-year-old girl walking in the Gleadless Road area was approached from behind by a man unknown to her.
The man is then said to have sexually assaulted her before running off in the direction of Myrtle Springs.
Officers believe this incident is linked to a second they are investigating.
An 18-year-old woman is reported to have been sexually assaulted on Sunday 21 April at 2.20pm, also in the Gleadless area.
Now, detectives investigating the two assaults want your help in identifying the man pictured as they believe he could hold important information.
Detective Constable Claire Franklin, investigating, said: “This investigation is a priority for officers in Sheffield CID and we are working hard to identify the man involved.
“So far we have carried out house-to-house enquiries and maximised CCTV opportunities in the area. Both victims are continuing to receive support from officers.
“I understand the concern local residents and the community will have around these incidents and I’d like to reassure them that we will continue to have an increased policing presence in the area.
“It’s vital that anyone who thinks they have seen a man acting suspiciously in the area contacts us.
“In addition, we also want to speak to the man pictured, who we believe will be able to assist with our enquiries. Do you recognise him?
“If you can help, please call 101 or Crimestoppers anonymously on 0800 555111 quoting incident number 506 of 24 April 2019.”