Johan ("Jon") Fredrik Wilhelm Haffner (born 2 March 1940) is a Norwegian surgeon and Professor Emeritus at the University of Oslo. He served as President of the Norwegian Medical Association from 1988 to 1991. His research has focused on the excitatory adrenergic response in gastric smooth muscle, and he has authored several textbooks and articles in his field. He is a son of , who was President of the Norwegian Medical Association 1954–1957.