Nissim ben Reuven (1290 – 9th of Shevat, 1376, Hebrew: נִסִּים בֶּן רְאוּבֵן) of Girona, Catalonia was an influential talmudist and authority on Jewish law.
[4] He suffered at the hands of certain wealthy and powerful Jews of his community, who even slandered him and other leading rabbis before the government,[5] and they were even imprisoned for a period of five months before their innocence was proven.
When the Spanish Jews combined to send a petition to the king entreating his protection, Nissim was one of the committee who drafted the document.
His best-known work is his commentary and explanation of Isaac Alfasi's Sefer Ha-halachot, which had, at that time, been adopted for practical decisions.
In his comments he did not hesitate to refute the greatest earlier authorities, such as Rashi, Rabbenu Tam, Maimonides, Nachmanides, and Solomon ben Aderet.
The extant commentaries of Nissim on the "Halakhot" cover the treatises Shabbat, Pesaḥim, Ta'anit, Rosh ha-Shanah, Beẓah, Sukkah, Megillah, Ketubot, Giṭṭin, Ḳiddushin, Shebu'ot, and Avodah Zarah.
He wrote a philosophical work containing twelve homilies ("derashot"), displaying in this small volume his familiarity with philosophy, especially with that of Maimonides and Ibn Ezra.