The victim, aged 17, was travelling on the number 36 bus from Harrogate to Ripon between 1pm and 2.15pm on Saturday 15 September 2012.
She sat at the very front of the bus on the top deck and wasn’t aware of anyone sitting behind her.
As the bus approached Ripon, the victim became aware of a man approaching her and, as they went past MacDonald’s, he touched her inappropriately.
Following the incident, the man got off the bus at the next stop and left in the direction of Lead Lane.
The man is described as white, around 18-years-old, with a slim build and short dark brown hair. He was wearing a red and blue checked shirt and had a dark coloured bag strapped across his body.
Officers are appealing to anyone who witnessed the incident or knows the identity of the person responsible to come forward.
PC Leah Champion, of Harrogate police, said:
This was clearly an upsetting experience for the victim and it is important that we identify the person responsible as soon as possible.
If you have any information about this incident, please contact the police or Crimestoppers.
Anyone who can help officers with their enquiries is urged to contact North Yorkshire Police on 101 – select option 2 – and ask for Leah Champion or Harrogate police. email firstname.lastname@example.org
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.
Please quote reference number 12120155573 when passing information about this incident.