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.