The Trek Speed Concept tri road bike was stolen at 10am on Wednesday 23 July 2014, outside a sandwich shop on Cold Bath Road.
The bike, which is blue and white, is valued at around £4,500, it also has oversized carbon tubing and distinctive tri-style handlebars.
The thief was seen riding the bike into Valley Gardens. He is described as a white man, aged in his early 20s, 5ft 10in tall and was wearing a white baseball cap, black hooded top and blue shorts.
PC James Skaith, of Harrogate Safer Neighbourhood Team, said: If you can help to identify the man whole stole the bike, I urge you to come forward and contact the police straight away.
I am also keen to speak to anyone who has seen the bike since the theft or knows where it is now and ask them to get in touch.
Anyone who can assist with this enquiry should contact Harrogate police on 101, select option 2 and ask for James Skaith. Alternatively, information can be emailed to firstname.lastname@example.org
Or call Crimestoppers anonymously on 0800 555111, quoting reference number 12140122523.