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).

Born in Winthrop, Massachusetts, Ditmar grew up in the Berkshire County city of Pittsfield, where he graduated from high school.

Ditmar won 47 games for the Yankees in a span of five years, with a career-high 15 in 1960, despite not getting to pitch on a regular basis in a rotation which included Whitey Ford, Bobby Shantz, Don Larsen and Bob Turley.

Ditmar defeated the Yankees 8–6, when the Athletics played their last game at Shibe Park in Philadelphia before moving to Kansas City.

After a Budweiser television commercial of the 1980s incorporated the original radio broadcast of the 1960 World Series Game 7, with announcer Chuck Thompson incorrectly naming Ditmar instead of Ralph Terry as the pitcher off whom Bill Mazeroski hit a home run, Ditmar sued Anheuser-Busch for $500,000, contending his reputation was tarnished.