At around 1am on Friday 30 September 2011, the 21-year-old victim was standing outside the ladies toilet of the Revolution bar, Wilmslow Road, Fallowfield when she was approached by a man.
He pushed her against a door and sexually assaulted her.
The man is described as being black, 5ft 8in tall, of medium build, clean shaved and wore blue jeans and blue t-shirt.
Now police have issued an image of a man wanted in connection with the incident.
Detective Constable Jennifer Wylde from Longsight CID said: “I would urge people to take a good look at this image and if they recognise the man to contact us straight away.
“The victim is still shaken by what happened that night and I would ask anyone who may have been at the bar and saw something take place to phone police.”
Anyone with information should phone police on 0161 856 4264 or the independent charity Crimestoppers, anonymously, on 0800 555 111.