Walter Joseph Kellner (April 26, 1929 – June 19, 2006) was an American relief pitcher in Major League Baseball who had an eight-year professional career, and played three games in the Major Leagues for the Philadelphia Athletics between 1952 and 1953. Kellner, 6 feet (1.8 metres) tall and weighing 200 pounds (91 kg) during his career, batted and threw right-handed. Kellner played several more years in the minors before retiring in 1958. He died in his hometown of Tucson, Arizona, on June 19, 2006.