Carl Hermann (17 June 1898 – 12 September 1961) was a German professor of crystallography. With Charles-Victor Mauguin, he invented an international standard notation for crystallographic groups known as the Hermann–Mauguin notation or International notation.
Born in the north German port town of Wesermünde to parents both of long-time ministerial families, he got his doctorate from Göttingen in 1923, as a pupil of Max Born and a fellow student with Werner Heisenberg. With Paul P. Ewald at Stuttgart, he nurtured the growing field of crystallography, especially the study of space groups, and began what was later to become Structure Reports, a reference series giving every known crystal structure determination.
When the Nazi Party rose to power, he objected to its political restrictions on academic positions, leaving to take a position as a physicist with industrial dye firm I.G. Farbenwerke at Ludwigshafen, where he continued his crystallographic research and studied symmetry in higher-dimensional spaces. During World War II, he and his wife Eva helped many Jews hide and escape the Holocaust, for which he was imprisoned and sentenced to death. As he was an eminent scientist with influential friends, the sentence was never carried out.
After the war, he lectured briefly at Darmstadt Polytechnic. Then, in 1947, he accepted a newly formed chair in crystallography at the University of Marburg, where he became director of the Crystallographic Institute and remained until his death.
He was an active Quaker and devoted much time to promoting international understanding.
In August 1994, the German Crystallographic Society (DGK) established the Carl Hermann Medal, its highest distinction, for outstanding contributions to the science of crystallography.