Officers from Hampshire Police are trying to trace him in connection with a sexual assault that occurred at a flat in the Newtown area in Southampton in the morning of Tuesday, Dec 1, 2015.
Police in Southampton have been conducting extensive enquiries to identify this man and are now asking the public for assistance.
The man is described as black, aged between 20 and 30 years old, wearing dark clothing and carrying a dark rucksack.
Detective Inspector John McGonigle from the Western Investigations Team said: "We believe this man was with the victim prior to her being assaulted and may have information highly relevant to our investigation.
"We would urge him or anyone who knows him to contact us and assist us with our investigation. Please make contact via 101 in confidence quoting 44150416954."
Alternatively, call Crimestoppers and leave information anonymously on 0800 555 111 or report online.