Robert James Fitzsimmons was a British professional boxer who was the sport's first three-division world champion. He also achieved fame for beating Gentleman Jim Corbett, and he is in The Guinness Book of World Records as the lightest heavyweight champion, weighing just 167 pounds when he won the title. Nicknamed Ruby Robert and The Freckled Wonder, he took pride in his lack of scars and appeared in the ring wearing heavy woollen underwear to conceal the disparity between his trunk and leg-development.

Professional boxing, or prizefighting, is regulated, sanctioned boxing. Professional boxing bouts are fought for a purse that is divided between the boxers as determined by contract. Most professional fights are supervised by a regulatory authority to guarantee the fighters' safety. Most high-profile bouts obtain the endorsement of a sanctioning body, which awards championship belts, establishes rules, and assigns its own judges and referees.