Australian yachtsman (yacht) and marine architect who designed Australia II, the first non-American yacht to win (1983) the prestigious America's Cup in the 132-year history of the race.

Lexcen, who had little formal education, was apprenticed at the age of 14 to a locomotive mechanic, but he eventually quit to build boats and sails. When he decided to abandon his manufacturing enterprise, he left his name (Bob Miller) with the company and had a friend's computer create a new six-letter surname for him. A self-taught boat designer and accomplished yachtsman, he represented Australia in the Soling class at the 1972 Olympic Games.

He first learned of the America's Cup challenge in 1970 while traveling in the United States with Alan Bond, a self-made millionaire and sailing enthusiast who commissioned Lexcen to design a boat that could beat the American entry. The result was Australia II, a yacht of the 12-metre class with a winged keel that improved the boat's stability and maneuverability. Lexcen suffered a heart attack in 1983 after accusations that he had not designed the revolutionary keel, but he ultimately received full credit for the boat's victory.