The woman was running along the cycle track behind Woodfield Road, sometime between 8pm and 9pm on Monday 26 August 2013, when she saw the man exposing himself in the bushes.
Officers are making enquiries to trace the man and are urging anyone who recognises him from the image to come forward with information.
He is described as white, in his early 20s, clean shaven, with strawberry blond hair and blue eyes.
He was wearing loose-fitting light blue jeans and a dark blue long-sleeved t-shirt.
Officers are appealing to anyone who also witnessed the man exposing himself or can help identify him to get in touch.
Anyone who can help officers with their enquiries is urged to contact North Yorkshire Police on 101 – select option 2 – and ask for PC Andy Hanson or Harrogate police.
Alternatively, information can be emailed to firstname.lastname@example.org
If you prefer not to give your name, Crimestoppers can be contacted anonymously on 0800 555 111.
Please quote reference number 12130149104 when passing information about this incident.