In Jewish law and history, Acharonim ((ʔ)aχ(a)ʁoˈnim; אחרונים Aḥaronim; sing. , Aḥaron; lit. "last ones") are the leading rabbis and poskim (Jewish legal decisors) living from roughly the 16th century to the present, and more specifically since the writing of the Shulchan Aruch (Hebrew: , "Set Table", a code of Jewish law) in 1563 CE.
The Acharonim follow the Rishonim, the "first ones"—the rabbinic scholars between the 11th and the 16th century following the Geonim and preceding the Shulchan Aruch. The publication of the Shulchan Aruch thus marks the transition from the era of Rishonim to that of Acharonim.
The Acharonim are thus contemporary with the Early Modern Period, the foundation of Hasidic Judaism, Jewish emancipation in Europe, the Haskalah (Jewish Enlightenment), Zionism, the Holocaust, the foundation of the State of Israel and the Jewish exodus from the Muslim world.
The distinction between the Acharonim, Rishonim and Geonim is meaningful historically. According to the widely held view in Orthodox Judaism, the Acharonim generally cannot dispute the rulings of rabbis of previous eras unless they find support from other rabbis in previous eras. Yet the opposite view exists as well:
In The Principles of Jewish Law Orthodox Rabbi Menachem Elon wrote:
Hilkheta Ke-Vatra'ei can be interpreted such that the Orthodox view does not constitute a contradiction, with an appeal to understand it within the greater context of Torah. While authority may go to the scholars of a later generation within a particular era, the Talmud does not allow scholars of a later era to argue with scholars of an earlier era without support from other scholars of an earlier era.
This is displayed in “hundreds of instances" in the Talmud in which Amora’im are challenged by Tanna’itic sources with the term מיתיבי and the Amorai'm unable to “deflect the challenge”. An Amora called Rav is challenged by Tannai’tic sources “and is vindicated by the statement, Rav tanna hu upalig”- “Rav is a Tanna and disagrees (in Eiruvin 50b, Kesubos 8a, and elsewhere).