Karl Ludwig Felix Machatschki (22 September 1895 – 17 February 1970) was an Austrian mineralogist. He was born in Arnfels (near Leibnitz) in Styria, Austria. He studied at the University of Graz, obtaining his habilitation in 1925; in 1927 he joined the group of Victor Goldschmidt in Oslo for one year. In 1930 he was appointed as a professor at the University of Tübingen. He changed university twice, first in 1941 to the University of Munich and finally in 1944 to the University of Vienna.