Høiby N. Louis Pasteur and the birth of microbiology in Denmark. APMIS 2022. Louis Pasteur's work initiated the birth of microbiology in Denmark. Carl Julius Salomonsen was the pioneer who inspired and taught Christian Gram, Thorvald Madsen and Bernhard Bang bacteriological techniques in his annual bacteriological course which he started in 1883 at the University of Copenhagen. These pioneers developed Danish human and veterinary microbiology and became world famous. Emil Chr. Hansen developed Danish technical/industrial microbiology in the Carlsberg Laboratory and purified yeast and designed equipment for the propagation of pure yeast which was used worldwide in beer brewing. He also became world famous. The fascinating birth and development of Danish microbiology is summarized in this article, which is dedicated to the 200th birthday of Louis Pasteur, December 27, and 100th birthday of the Danish Pasteur Society, October 25, 2022.