Nina Karlovna Bari (Russian: Нина Карловна Бари; 19 November 1901 – 15 July 1961) was a Soviet mathematician known for her work on trigonometric series.

As a student, Bari was drawn to an elite group nicknamed the Luzitania—an informal academic and social organization.

She then attended the Polish Mathematical Congress in Lwów, Poland; a Rockefeller grant enabled her to return to Paris to continue her studies.

By 1930, all traces of the Luzitania movement had vanished, and Luzin left Moscow State for the Academy of Science's Steklov Institute of Mathematics.

In 1932, she became a professor at Moscow State University and in 1935 was awarded the title of Doctor of Physical and Mathematical Sciences, a more prestigious research degree than traditional Ph.D.[2] By this time, she had completed foundational work on trigonometric series.

[6] It was possibly a suicide due to depression caused by Luzin's death eleven years earlier.