Philip Herries Gregory FRS (24 July 1907, Exmouth, Devon, UK – 9 February 1986) was a British mycologist and phytopathologist.

[1] During childhood, as a result of severe asthma which prevented him from regular school attendance, Philip H. Gregory had an erratic early education.

There he did research in botany under the supervision of the plant pathologist William Brown and graduated with a Ph.D. on Fusarium disease in the genus Narcissus.

[3] During WW II he served as an air raid warden and during nights on duty he read scientific literature relevant to his research.

He found a 56-page paper on dissemination of infectious diseases of plants by air currents, published by Konstantin Mikhailovich Stepanov [ru] in 1935 in Russian.

Gregory thereupon learned Russian from phonograph records which he purchased with money received from selling his grandfather's gold watch.

Gregory became interested in the production of penicillin by Penicillium chrysogenum Thom (then known as P. notatum Westling) and took a one-year secondment to work at Imperial Chemical Industries, Ltd., Biological Laboratories, Manchester.

[15] In 1953 Gregory resigned his position as assistant director of Rothamsted's plant pathology laboratory to become a professor in the chair of botany at Imperial College London.

[1] Gregory was a leading expert on aerobiology related to fungal spores, but he also did important research on "dermatophytes, flowering bulbs, the spread of potato viruses, human allergy and cocoa diseases".