Aryeh Tzvi Frumer (Hebrew: אריה צבי פרומר; also spelled Fromer or Frommer; 1884 – 2 May 1943)[2] was a leading Orthodox rabbi, rosh yeshiva, and posek (halachic authority) in 20th-century Poland.

[3][4] In 1913 Frumer published his first book, Siach HaSadeh, a series of essays explaining topics in the Gemara, especially those in Seder Moed.

[3] At war's end, when the second Sochatchover Rebbe relocated to Zgierz, Frumer succeeded his uncle, Rabbi Yitzchok Gutensztain, as Rav of Koziegłowy.

[4][5] Frumer was forced to leave the city in 1921,[2] either due to the enmity of a neighboring priest or a disgruntled rich man who had lost a din Torah.

[4] Frumer brought "a new spirit of scholarship, righteousness, and depth" to the hundreds of exceptional students at Yeshivas Chachmei Lublin.

[4] In 1938 he published his second work, ארץ צבי (Eretz Tzvi) (the title being another name for the Land of Israel and a play on his own name), a book of responsa concerning practical laws in the Shulchan Aruch, section Orach Chaim.

[2][5] It has been noted for its unique approach to halacha, using non-halakhic and kabbalistic sources to solve halachic problems,[5] and is still widely quoted to this day.

Frumer also produced an anonymous pamphlet titled עיקרי דיני תפילה (Main Laws of Prayer), which was widely read in prewar Poland.

[9] As the Nazi deportations increased in frequency, Frumer and his Rebbe joined other Torah scholars who disguised themselves as workers in a large shoe factory owned by Fritz Schulz.