Olin James Stephens II (April 13, 1908 – September 13, 2008) was an American yacht designer of the 20th century. Stephens was born in New York City, but spent his summers with his brother Rod, learning to sail on the New England coast. He also attended the Massachusetts Institute of Technology for a term.
Stephens' name had a long history in connection with America's Cup. He assisted W. Starling Burgess with the design of the J-Class Ranger, which won the America's Cup in 1937, defeating the Royal Yacht Squadron's Endeavour II in four races. He was the original designer of six out of seven successful 12 Metre defenders of the America's Cup between 1958 and 1980, with the exception of Weatherly in 1962. Other than Ranger, the most remarkable of his defenders was the Intrepid. She had a rudder separate from her keel to reduce wetted surface and improve steering. Stephens had previously designed separate rudders on a number of increasingly large ocean racers of the 1960s, most notably Thomas Watson's state of the art Palawan III, before using it successfully on the Intrepid in 1967. After alterations by Britton Chance, Jr., she won the America's Cup again in 1970.
Stephens also designed many off-shore and stock boats, including the Dark Harbor 20, which he designed in 1934. His brother, Roderick Stephens, was also a partner in the yacht-designing and yacht brokerage firm Sparkman & Stephens, specializing in supervision and testing of yachts designed by the firm. Olin was working in the Nevins shipyard in 1928 as a draftsman when he first met yacht broker Drake Sparkman. They together set up an office next door to Nevins in 1929. Since retiring from the company he lived in Hanover, New Hampshire, where he spent his final years writing computer programs for designing yachts. He was awarded the Herreshoff Award by the North American Yacht Racing Union in 1965 for his contributions to sailing.