Johan Martin Ferner (né Johan Martin Jacobsen; 22 July 1927 – 24 January 2015) was a Norwegian sailor and Olympic medalist. He won a silver medal in the 6 metre class with the boat Elisabeth X at the 1952 Summer Olympics in Helsinki, together with Finn Ferner (his brother), Erik Heiberg, Tor Arneberg and Carl Mortensen. He was married to Princess Astrid, the sister of King Harald V of Norway. He was also the brother-in-law of Princess Ragnhild.