Reuben ben Mordecai Brainin (Hebrew: ראובן בריינין, romanized: Reuven Brainin; March 16, 1862 – November 30, 1939) was a Russian Jewish publicist, biographer and literary critic.

[2] Brainin contributed to the periodicals Ha-Meliẓ, Ha-Toren, Ha-Ẓefirah, Ha-Maggid, and Ha-Shiloaḥ.

In 1895 he issued a periodical under the title "Mi-Mizraḥ u-Mi-Ma-arav" (From East and West), of which only four numbers appeared.

Brainin was the author of several pamphlets, the most important of which were his sketch of Pereẓ Smolenskin's life and works (Warsaw, 1896); and a translation of M. Lazarus' essay on Jeremiah (Warsaw, 1897).

He also wrote about one hundred biographical sketches of modern Jewish scholars and writers.