Walter Friedrich Karl Weizel (1 August 1901 in Lauterecken – 6 August 1982) was a German theoretical physicist and politician. As a result of his opposition to National Socialism in Germany, he was forced into early retirement for a short duration in 1933. He was a full professor at the University of Bonn, from 1936 to 1969. After World War II, he helped to establish the Jülich Research Center, and he was a state representative of the Social Democratic Party of Germany.
From 1918 to 1925, Weizel studied chemistry at the Georg-August-Universität Göttingen, the Ludwig-Maximilians-Universität München, and the Ruprecht-Karls-Universität Heidelberg. He received his doctorate in physical chemistry at Heidelberg, under Max Trautz. He switched form chemistry to physics to work on the quantum mechanics of molecules as a fellow of the Notgemeinschaft der Deutschen Wissenschaft (NG; Emergency Association of German Science) at the . He completed his Habilitation in 1929.
After Habilitation, Weizel worked briefly at Badische Anilin- und Sodafabrik (BASF, Baden Aniline and Soda Factory) at Ludwigshafen. Then, during 1931, he had a Rockefeller fellowship to the University of Chicago.
From late in 1931, Weizel was an ordentlicher Professor (ordinarius professor) of theoretical physics at the Technische Hochschule Karlsruhe (today, the University of Karlsruhe). After Adolf Hitler came to power in 1933, Weizel was temporarily forced into retirement due to his opposition to National Socialism. In 1936, he was called from the Technische Hochschule Karlsruhe to an ordinarius professorship at the Rheinische Friedrich-Wilhelms-Universität Bonn.