John O. "Kick" Kelly (October 31, 1856 – March 27, 1926), also nicknamed "Honest John" and "Diamond John," was an American catcher, manager and umpire in Major League Baseball who went on to become a boxing referee and to run gambling houses in his native New York City. He made a notable impact on the development of umpiring, helping to pioneer the use of multiple umpires in games in the 1880s.