Arthur John Ditmar (April 3, 1929 – June 11, 2021) was an American starting pitcher in Major League Baseball who played with the Philadelphia / Kansas City Athletics (1954–56, 1961–62) and the New York Yankees (1957–61).

Ditmar batted and threw right-handed and was listed at 6 feet 2 inches (1.88 m) tall and 185 pounds (84 kg).