Justus Carl Hasskarl (6 December 1811 – 5 January 1894) was a German explorer and botanist specializing in pteridophytes, bryophytes and spermatophytes.

Subsequently, he sent a request to the governor general to work in the National Botanical Garden and a year later he was appointed assistant curator.

[2] With director Johannes Elias Teijsmann, they rearranged their crops to taxonomic families, which would result in the displacement of many specimens in the botanical garden.

Together they organized expeditions to various parts of modern Indonesia and expand the number of plants collection in the Botanic Garden.

[3] In 1852, the Netherlands government sent him to Lima and in early 1853, Justus made an expedition to the interior of Peru and even reaching the eastern border of Lake Titicaca, where he gathered Cinchona trees for Malaria treatment.