They made the appeal after recently receiving a report of an incident which allegedly happened in 1973 in Belfast involving a girl in her early teens and a number of men.
The police say they recognise it may be daunting for the victim to come forward but have assured they will give their full support.
Detective Inspector Carol Dane said: “Police recently received a report that a young girl had been the victim of a serious sexual assault in a communal area of Unity Flats on January 1, 1973.
“While our investigation is at a very early stage we believe the girl would have been aged in her early teens at the time of the incident and a number of men are reported to have been involved.
“I am making a direct appeal for the victim of this attack to come forward and speak with detectives at Musgrave Police Station.
“We understand it is daunting to come forward to Police but please be assured that we will support you and work alongside you, at your pace, as we carry out our investigation.
“You do not need to come into a police station to make a report. You can report directly to us via 101 or through a dedicated email address at [email protected] and detectives, who are specially trained in this work, will arrange to meet you at a time and place that best suits you.
“I can assure you that you will be treated with the utmost sensitivity, care and respect.
“Please don’t suffer in silence, there are specially trained professionals who can help you,” Detective Inspector Dane said.
If you are victim of historical child sexual abuse, support is available through:
* The 24 Hour Domestic & Sexual Abuse Helpline - 0808 802 1414
* Nexus NI - 028 9032 6803 http://nexusni.org/
* The Rowan Centre free phone helpline - 0800 389 4424 / www.therowan.net
* Victim Support NI - 02890 243133