The 19-year-old was attacked at Quay Street on Saturday night, September 21.
Mayor Andrew Muir said: “This was a despicable attack right in the heart of Bangor, which will be guaranteed to send shock waves through the local community.
“My thoughts are with the victim at this difficult time.
“I would urge anyone with information about this sexual assault to contact the police as soon as possible. The perpetrator of this crime must be removed from our streets.”