Walter Kossel (4.01.1888-22.05.1956) was a German experimental physicist. He was born in Berlin. He graduated from the University of Heidelberg (1911). He worked at the University of Munich; in 1921—32 he was professor at the University of Kiel and director of the Institute of Theoretical Physics, and in 1932 —47 at the Higher Technical School in Danzig and director of the Institute of Experimental Physics. From 1947 he was professor and director of the Physics Institute in Tübingen.
His research concerned spectroscopy, the theory of the chemical bond and of the periodic system of the chemical elements, the diffraction of X-rays and of electrons, electric discharges in gases, solid-state physics and the physics of crystals. He explained the origin of X-ray spectra (the Kossel theory), chemical interactions and the nature of the chemical bond. In 1916 he showed that the chemical properties of atoms are determined by the number of valence electrons in the outer electron shell. Together with A. Sommerfeld he established the spectroscopic displacement law. He discovered the interference of characteristic X-rays (the Kossel effect).