According to Victoria police, the incident occurred on a bus in Springvale, south-east of Melbourne on August 28.
Police have been told that an 18-year-old woman boarded a 902 bus to Chelsea about 1.40pm.
Police believe that a man aged in his 30s perceived to be Indian in appearance sitting opposite the woman allegedly began rubbing himself inappropriately and exposed himself to her before alighting the bus near Harold Street in Springvale South.
Transit Crime Investigation Unit detectives are appealing for public assistance in relation to the incident.
Victoria police have also released the CCTV image of the man they think may be able to assist with their enquiries.
The man has been described as a medium build with dark hair and unshaven/light beard. He who was carrying a black backpack was wearing a striped top with dark coloured denim jeans, says police.
CCTV Image of man released by Victoria Police Source: Victoria Police
Police have urged that anyone with information or have witnessed the willful and obscene exposure may contact Crime Stoppers on 1800 333 000 or submit a confidential report at www.crimestoppersvic.com.au
