The walker, whose age has not been disclosed, was reported to be ill in a forest north of Helmsley in the North York Moors yesterday.
Fourteen mountain rescue volunteers were sent to the scene, but the man was pronounced dead.
His body was recovered to the nearest road by North Yorkshire Police.
Cleveland Mountain Rescue Team said: "Our thoughts are with the gentleman’s family and friends at this very sad time. We would also like to pass on our thanks to local farmers who assisted us by providing a parking area and with access across their land.
"Fourteen team members were involved including one person co-ordinating our response from home. The call-out lasted approximately five hours including travel time for our volunteer members to return to their homes and places of work and for our Land Rover crew to return to base to be ‘call-out ready’ once again."