William Webster Diehl (January 15, 1891 – 1978) was an American mycologist recognized for his work on grass pathogens, particularly in the genus Balansia.
The family moved to Ohio shortly after his birth and he attended grammar school in Dayton.
[1] He attended Miami University from 1910–1914 and received an MSc in botany from Iowa State College in 1915.
[2] He was briefly an instructor of botany and plant pathology with Clemson before joining the USDA where he worked from 1928 until his retirement in 1958.
[2] Together with Flora Wambaugh Patterson and Edith Katherine Cash he issued the exsiccata-like series Mycological exchange of 1921 with specimens distributed by the USDA.