Walther Ludwig Julius Kossel (4 January 1888 in Berlin, Germany – 22 May 1956 in Tübingen, Germany) was a German physicist known for his theory of the chemical bond (ionic bond/octet rule), Sommerfeld–Kossel displacement law of atomic spectra, the Kossel-Stranski model for crystal growth, and the Kossel effect. Walther was the son of Albrecht Kossel who won the Nobel Prize in Physiology or Medicine in 1910.