Sergei Natanovich Bernstein (Russian: Сергей Натанович Бернштейн, sometimes Romanized as Bernshtein) (March 5, 1880 - October 26, 1968) was a mathematician who was born in Odessa, Imperial Russia and died in Moscow, USSR.
His doctoral dissertation, submitted in 1904 to the Sorbonne, solved Hilbert's nineteenth problem on the analytic solution of elliptic differential equations. Later, S.B. published numerous works on Probability theory, Constructive function theory, mathematical foundations of genetics, et cet. From 1906 until 1933, Bernstein was the leading light of the Kharkov Mathematical Society.