A man in his 20s reported being raped within an address in Tiber Street in the early hours of Saturday morning (October 2).
Detectives have now released CCTV images of a man they would like to trace as part of their investigation.
Officers said the man - who spoke to the victim earlier in the night near Blitz Nightclub in Church Row - may hold "vital information".
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Det Insp George Binns, from Preston Police, said: "We have undertaken a number of enquiries including combing through CCTV and as a result, we would like to speak to the man pictured as he may hold vital information that could assist our investigation, particularly as we know he has been in conversation with the victim earlier in the night close to Blitz Nightclub.
"If this could be you or someone you know, please get in contact with us as soon as possible.
"Similarly, if you know anything about the incident, we need to speak to you."
Anyone with information can call 101, quoting incident reference number 1250 of October 2, 2021.
You can also report any information online at doitonline.lancashire.police.uk.
Alternatively, independent charity Crimestoppers can be contacted anonymously on 0800 555111 or online via crimestoppers-uk.org.
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