Karl (or Carl) Wilhelm Leopold Krug (January 7, 1833 – April 4, 1898) was a German businessman, naturalist, ethnographer, diplomat and supporter of scientific collections.
Born on the estate of Mühlenbeck in the vicinity of Berlin on January 7, 1833, he was educated by private tutors and in several schools (gymnasia), obtaining his matriculation certificate in 1854.
Under the influence of his legal advisor Don Domingo Bello y Espinoza, Krug became an avid collector of plants and insects.
Krug and (to some extent the Berlin Academy of Sciences) underwrote the collecting expeditions of Paul Sintenis and of the baron Eggers, at the time commanding officer of the Danish forces on St. Thomas.
These, together with his own extensive material and other acquisitions became the basis of the Herbarium Krug et Urban, which was destroyed in the Second World War.