McDiarmid (July 29, 1869 – May 13, 1942)[1] was an American attorney who was the principal owner of the Cincinnati Reds of Major League Baseball.

McDiarmid was born in July 1869 in Barnesville, Ohio, and spent much of his childhood in Ontario.

[2] In addition to practicing law, he played semi-professional baseball as a pitcher.

[6][7] Late in the 1929 season, Sidney Weil acquired enough shares to become the controlling owner of the Reds.

[8] McDiarmid died in Wyoming, Ohio, in May 1942; he was survived by his wife, three daughters, and two sons.