Ernest Guy Diehl (October 2, 1877 – November 6, 1958) was a Major League Baseball outfielder who played for four seasons.

He played for the Pittsburgh Pirates from 1903 to 1904, and the Boston Beaneaters/Doves in 1906 and 1909.

He served as the head baseball coach at the University of Cincinnati in 1910.

[1] Diehl also played tennis.

This biographical article relating to an American baseball outfielder born in the 1870s is a stub.