Police are hunting a sexual predator who ‘repeatedly sexually assaulted’ a woman on a train in Melbourne’s north in May.

During the incident, which occurred on May 16, a woman boarded a city-bound train at Thornbury Railway Station about 9.35am and was repeatedly sexually assaulted during the commute.

The 49-year-old woman moved away from the man several times but he continually followed her.

She got off the train at Flagstaff Station and he continued to follow her and engage in conversation.

She notified station staff and the offender left the station.

The man is believed to be of Islander or Asian appearance, 20-25-years-old, approximately 160cm tall, slim build and a thin moustache.

He was wearing a navy New York Yankees baseball cap, navy baseball style jacket with white sleeves and beige pants.

There will be an information caravan set up today between 7am and 11am at Thornbury Railway Station, for anyone who might have information about the offender or the incident.