Ludvig Dmitrievich Faddeev (also Ludwig Dmitriyevich; Russian: Лю́двиг Дми́триевич Фадде́ев) (23 March 1934 – 26 February 2017) was a Soviet and Russian theoretical physicist and mathematician. He discovered of the Faddeev equations in the theory of the quantum mechanical three-body problem and for the development of path integral methods.
Faddeev led the Leningrad School, in which he along with many of his students developed the quantum inverse scattering method for studying quantum integrable systems in one space and one time dimension. This work led to the invention of quantum groups by Drinfeld and Jimbo.
From 1976 to 2000, Faddeev was head of the St. Petersburg Department of Steklov Institute of Mathematics of Russian Academy of Sciences (PDMI RAS).