Robert James "Bob" Fitzsimmons (May 26, 1863 – October 22, 1917) was a British professional boxer of Irish and Cornish descent who made boxing history as the sport's first three-division world champion. He also achieved fame for beating Gentleman Jim Corbett, the man who beat John L. Sullivan and is in The Guinness Book of World Records as the lightest Heavyweight Champion. 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. He was also known for his pure fighting skills due to dislike of training for fights, which would ultimately cost him at times in his career.
Fitzsimmons is ranked as #8 on Ring Magazine's list of 100 greatest punchers of all time.