Isser Zalman Meltzer (1870 – November 17, 1953), was a famous Lithuanian Orthodox rabbi, rosh yeshiva and posek. He is also known as the "Even HaEzel"—the title of his commentary on Rambam's Mishne Torah.
Rabbi Meltzer was born in the city of Mir, in what is today Belarus. His father, Baruch Peretz, was also a rabbi. From the age of 10, he studied with Rabbi Yom-tov Lipman, the rabbi of the city, and at the Mir Yeshiva. At the age of 14, he began studying at the Volozhin yeshiva under the Netziv and Rabbi Chaim Soloveitchik, where he remained for seven years.
While at the yeshiva, he became involved in the secret [Orthodox] Ness Ziona Society, part of the Hovevei Zion movement. Together with his brother-in-law, Rabbi Moshe Mordechai Epstein, he contributed to the founding of the city of Hadera by buying land for an etrog orchard.
In 1894, Rabbi Melzer became a maggid shiur at the Slabodka yeshiva, together with his brother in law, Rabbi Epstein. In 1897, Rabbi Meltzer left Slabodka to lead another yeshiva which had been established by the Ridvaz in Slutsk.
In 1903, Rabbi Meltzer was appointed as the Rabbi of Slutsk, a position he held for 20 years. Although he had already been serving as the rosh yeshiva in that city, he had no document of semicha because he had never planned on accepting a position in the rabbinate, but to teach Torah instead. When the communal leaders resolved to appoint him as their rabbi, Rabbi Meltzer wrote to his teacher Rabbi Chaim Soloveitchik and to Rabbi Yechiel Michel Epstein, author of the Arukh HaShulkhan, asking them to send him the necessary affirmation. Rabbi Epstein immediately mailed him a letter of semicha, while Rabbi Soloveitchik made do with a brief telegram that simply bore the words, "Yoreh yoreh, yodin yodin".