Léon Charles Albert Calmette ForMemRS (12 July 1863 – 29 October 1933) was a French physician, bacteriologist and immunologist, and an important officer of the Pasteur Institute. He discovered the Bacillus Calmette-Guérin, an attenuated form of Mycobacterium used in the BCG vaccine against tuberculosis. He also developed the first antivenom for snake venom, the Calmette's serum.