Bar-Ilan was born Meir Berlin in 1880 to a Lithuanian Jewish family, the youngest son of Rabbi Naftali Zvi Yehuda Berlin and his second wife Batya Miriam Berlin. Bar-Ilan's father was the head of the famous Volozhin Yeshiva in Lithuania. Bar-Ilan was also a descendant of Rabbi Meir Katzenellenbogen, the Maharam of Padua. He studied at the Volozhin Yeshiva and, after his father's death in 1894, at the traditional yeshivas of Telshe, Brisk and Novardok, where he learned with his maternal grandfather, Rabbi Yechiel Michel Epstein. After gaining semicha in 1902 at the age of twenty-two, Bar-Ilan travelled to Germany to attend the University of Berlin. There, he became acquainted with a more modern form of Orthodox Judaism that had a more tolerant attitude to secular education and to political Zionism. Bar-Ilan was deeply influenced by the local religious community and its philosophy of Torah im Derech Eretz.
In 1905 Bar-Ilan joined the Mizrachi movement, representing it at the Seventh Zionist Congress, at which he voted against the Uganda Proposal to create a temporary Jewish homeland in British East Africa, as suggested by Great Britain. In 1911, he founded the Hebrewweekly newspaperHa’Ivri in Berlin as a "non-party paper dedicated to all the affairs of Israel, faithful in its spirit to our religious tradition and to our national renaissance." That same year, Bar-Ilan was appointed secretary of the world Mizrachi movement. In 1913 he came to the United States and developed local Mizrachi groups into a national organisation, chairing the first American Mizrachi convention, held in Cincinnati in May 1914. Bar-Ilan settled in New York in 1914, becoming president of the American Mizrachi movement the following year, a position he held until 1928. In his absence Ha’Ivri ceased publication in April 1914, but was re-established under Bar-Ilan's direction in New York in January 1916. Published until 1921, the paper's contributors included such prominent writers as S. Y. Agnon, Joseph Opatoshu, Reuben Brainin, Eliezer Ben-Yehuda, and Yehuda Leib Maimon. Bar-Ilan was also an active member of the Joint Distribution Committee during World War I, and served as vice president of the Central Relief Committee of New York City in 1916. He founded the Mizrachi Teachers Institute in 1917. From 1920 through 1922, Bar-Ilan briefly served as acting president for what is now Yeshiva University during the temporary absence of its then-president, Bernard Revel.
Along with Rabbi Shlomo Yosef Zevin, Bar-Ilan was the editor of the Talmudical Encyclopedia, Volumes I and II. He also wrote articles on Talmudic subjects for various periodicals. Notable works of Bar-Ilan include:
Fun Volozhin biz Yerushalayim, autobiography in two volumes
Bishvil ha-Techiah
Raban shel Yisrael
After 1948, his activities were scholastically oriented. He organized a committee of scholars to examine the legal problems of the new state in the light of Jewish law and founded an institute for the publication of a new complete edition of the Talmud.
Legacy
Bar-Ilan inspired the founding of Bar-Ilan University in Ramat Gan by the American Mizrachi movement, named in his honour. The moshav Beit Meir is named in his honour, as are the Meir Forest in the Hebron Hills and Bar-Ilan Street in Jerusalem.