The incident took place around 4pm on October 1 on the 55 Stagecoach bus from Calne to Swindon.
An older man sat opposite a teenage girl and inappropriately touched her multiple times.
He is described as being aged in his 40s or 50s, Asian and was wearing a zipped hooded top.
We would like to hear from anyone who saw what happened. If anyone has any further information please contact 101 quoting reference number 54230109844.
