Reuben Margolies, (Hebrew: ראובן מרגליות) (November 30, 1889 – August 28, 1971) was an Israeli author, Talmudic scholar and head of the Rambam library.

Margolies was born in 1889 in Lemberg (now Lviv), then part of the Austrian-Hungarian Empire and now in Ukraine and from 1918 to 1940 in Poland.

He possessed a photographic memory, and was well versed in all aspects of both the written Bible, Oral Torah (Talmud and its commentaries) and Kabbalah (Zohar etc.).

He wrote a number of scholarly biographies of major Jewish personalities such as Maharsha, Ohr Ha-Chaim Hakodosh, Noam Elimelech, Moses ben Nachman (Ramban), and Yechiel of Paris.

There is also a memorial volume edited by Yitchak Raphael and published by Mossad R' Kook, which describes these and more books in more detail.