In the weight sensitive sport of boxing, Jack Dillon, "The Giant Killer," was considered an anomaly. Size was irrelevant; besides, it was only a factor if he accepted as such. He refused. Sturdy, compact and indestructible, yet capable of turning on a dime, Dillon not only defeated his opponents, he humiliated them. This dynamic defined his prolific and unparalleled career (1908-1925). His accepted record of 94-7-14, with 129 no decisions and one no contest (64 victories by way of knockout), put him in elite company with other members of the International Boxing Hall of Fame. While he claimed the middleweight championship for over two years, the unrivaled Hoosier pugilist was often recognized as the world light heavyweight champion. Moving up a division, he disposed of heavyweight contenders like tissues during flu season. On June 29, 1916, Dillon defeated Frank Moran and was clearly the top contender for giant Jess Willard's heavyweight crown. Yet, Willard, who outweighed Dillon by 60 pounds, and was about a foot taller, refused. This first biography of the celebrated pugilist is based on contemporaneous newspaper accounts of the time and includes several appendices with career statistics and a selected boxing record.