Leonid Isaakovich Mandelshtam (Леонид Исаакович Мандельштам, last name more often spelled as Mandelstam) (May 4, 1879 - November 27, 1944) was a Russian/Soviet physicist of Jewish background.
Mandelshtam was born in Mogilev, Russian Empire (now Mahilyow, Belarus).
He was mentor to a Nobel Laureate in Physics Igor Yevgenyevich Tamm in science and life and created one of two major schools of theoretical physics in Soviet Union (another being due to Lev Landau). The main emphasis of his work was broadly considered theory of osillations, which included optics and quantum mechanics. He was a co-discoverer of inelastic scattering of light used in Raman spectroscopy. The actual discovery (together with Grigory Landsberg) was done in parallel or even earlier than that of Raman (and K. S. Krishnan ) and in Russian literature it is called "combination light scattering" (from combination of frequencies).
Mandelshtam died in Moscow, Soviet Union (now Russia).
References
Feînberg, E.L. The forefather Uspekhi Fizicheskikh Nauk, Vol. 172, 2002 (Physics-Uspekhi, Vol. 45, 2002)