Karl Johannes Kniep (3 April 1881 - 17 November 1930) was a German botanist who was a native of Jena.
He studied medicine at the University of Kiel, and botany in Jena with Christian Ernst Stahl (1848-1919), where he received his doctorate in 1904. In 1905 he became an assistant to Wilhelm Pfeffer (1845-1920) at the University of Leipzig, and afterwards performed research on the physiology of algae in Bergen. Starting in 1907, he was a private lecturer at the University of Freiburg, and in 1911, became a professor at the University of Strasbourg.
In 1914 Kniep became a full professor at the University of Würzburg, where he was also deacon of the university in 1923-24. In 1924 he succeeded Gottlieb Haberlandt (1854-1945) as professor of plant physiology at the University of Berlin. Beginning in 1916, he was editor of the Zeitschrift für Botanik (Magazine of Botany).
Hans Kniep is remembered for his research concerning the cytology and genetics of fungi, and particularly his investigations of the developmental history of Basidiomycota. Between 1913 and 1917, he published five treatises involving the origin, genetics and developmental history of a unique class of fungi known as Hymenomycetes. He also did extensive studies of the physiology, chemotaxis and photosynthesis of marine plants.