Officers are appealing for information as to the whereabouts of Jonathan Cowels.
Jonathan, 38 from Northallerton, was last seen in the town at 2pm on Friday 8 September 2017.
He was riding his silver Boardman mountain bike and was last seen wearing a black cycling jacket with white reflective stripes and dark cotton knee length shorts.
Anyone who has seen Jonathan or who has any information as to where he might be is asked to contact North Yorkshire Police.
Dial 101, press 1 and pass information to the force control room.
Please quote reference 12170161698 when passing on any information.