Transit Crime Investigation Unit detectives are investigating a sexual assault on tram route 70 to Melbourne CBD earlier this year, Victoria Police say.
Investigators have been told a 23-year-old woman boarded the tram with family and friends outside Flinders Street Railway Station about 7pm on 25 July.
Due to an event being held in the CBD and a high number of regular commuters, the tram was heavily congested and the victim initially stood face to face with the male suspect.
The man moved around the victim before he sexually assaulted her.
The victim attempted to move away from the man but due to limited space on the tram carriage, she was unable to remove herself from the situation and the man continued to assault her.
The woman ultimately pushed away from the man and informed her family and friends of the assault.
An unknown commuter also on the tram at the time of the incident then told the man to leave the area.
The man then disembarked at William Barrack Bridge.
The man is believed to be aged in his 50s or 60s and is described as being of an Indian sub continental or African appearance with a shaved head and distinctive gold capped teeth
He was wearing business attire and a camel coloured trench coat.
Detectives have released a composite image of a man they believe can assist with their enquiries and the distinctive gold capped teeth of the male suspect.
Anyone with information is urged to contact Crime Stoppers.