Detectives need to speak to Gheorghe Mighali, 27, of no fixed abode, to assist the investigation.
A photograph of Mr Mighali, a Romanian national, has been circulated to all police forces and the media to help trace him.
He is known to have visited the Whitby area on or around Tuesday 5 March. He was seen in Middlesbrough on Thursday 7 March, in Hartlepool on Friday 8 March and Newcastle on Tuesday 12 March.
He is described as white, slim build, 5ft 5in tall, long dark hair and with a pronounced nose and full lips.
The incident in Whitby occurred in the Stakesby Road and Station Avenue area between 9pm and 10pm on Saturday 9 March. The victim, who is aged in her mid-teens, was approached and sexually assaulted by an unknown man.
Police enquiries remain ongoing to establish the full circumstances surrounding the incident.
Detective Chief Inspector Andrea Kell said:
I am appealing for people to contact the police if they have seen Gheorghe Mighali or a man matching his description.
He was last seen in Newcastle on Tuesday 12 March but it is possible that he could be using public transport to visit any part of the country.
If you can help us trace him, please contact the police as soon as possible.
Please call North Yorkshire Police on 101, select option 1 and pass details to the Force Control Room.
If you would prefer to remain anonymous, information to assist the investigation can be forwarded to Crimestoppers on 0800 555 111. Please quote reference number 12130038977.