John Richard Gelnar (born June 25, 1943) is an American former Major League Baseball pitcher. Gelnar attended in Granite, Oklahoma, and the University of Oklahoma, where he played college baseball for the Oklahoma Sooners. He signed with the Pittsburgh Pirates as an amateur free agent in 1963, after his freshman year at Oklahoma. His contract was purchased by the Kansas City Royals from the Pirates after the 1968 season, but he was traded by the Royals with Steve Whitaker to the Seattle Pilots for Lou Piniella prior to the 1969 season. He was traded by the Brewers with José Herrera to the Detroit Tigers for Jim Hannan in 1971.