Who was the first Olympic gold medalist to win a professional heavyweight world boxing title?

Floyd Patterson (January 4, 1935 – May 11, 2006) was an American professional boxer who competed from 1952 to 1972, and twice reigned as the world heavyweight champion from 1956 to 1962. At the age of 21, he became the youngest boxer in history to win the title, and was also the first heavyweight to regain the title after losing it. As an amateur, he won a gold medal in the middleweight division at the 1952 Summer Olympics held in Helsinki, Finland.

Although Patterson fought around the light heavyweight limit for much of his early career, he and manager Cus D'Amato always had plans to fight for the Heavyweight Championship. In fact, D'Amato made these plans clear as early as 1954, when he told the press that Patterson was aiming for the heavyweight title.

After beating Tommy "Hurricane" Jackson in an elimination fight, Patterson faced former Light Heavyweight Champion Archie Moore on November 30, 1956, for the World Heavyweight Championship. He beat Moore by a knockout in five rounds and became the World Heavyweight Champion. He was the first Olympic gold medalist to win a professional heavyweight title.