chemist who discovered the Walden inversion, a reversal of stereochemical configuration that occurs in many reactions of covalent compounds.

Walden went to Germany after the Russian Revolution of 1917 and served as head of the chemistry department of the University of Rostock from 1919 to 1934. He became professor of chemistry at the University of Tübingen in 1947. Walden is also responsible for Walden's rule, which relates the conductivity and viscosity of nonaqueous solutions.