Paul-Marie-Léon Regnard (7 November 1850 – 18 April 1927)[1] was a French physician, physiologist and photographer.

He was one of the first naturalists to study the effects of atmospheric pressure on microbial metabolism.

[2] In 1878 he received his medical doctorate, and was later appointed director of the Institut national agronomique (1902).

[3] Regnard, an early practitioner of medical photography, is also known for the photographs he took of the mentally ill at La Salpêtrière hospital in Paris, published in the book Iconographie photographique de la Salpêtrière.

[4] His photographic work is included in the permanent collections of the Museum of Fine Arts Houston,[7] the San Francisco Museum of Modern Art,[8] the Wellcome Collection[9] and the Getty Museum.