The Union of Orthodox Jewish Congregations of America

Hechsher of the Orthodox Union
The hechsher of the Orthodox Union is the most widely known hechsher in the United States
Expansion	Orthodox Union
Certifying agency	Kosher Division of Orthodox Union
Product category	Food products
Type of standard	Religious

The Union of Orthodox Jewish Congregations of America (UOJCA), more popularly known as the Orthodox Union (OU), is one of the oldest Orthodox Jewish organizations in the United States. It is best known for its kosher certification service. Its circled-U symbol, Ⓤ, a hechsher mark, is found on the labels of many kosher commercial and consumer food products.

The OU supports a network of synagogues, youth programs, Jewish and Religious Zionist advocacy, programs for the disabled, localized religious study programs, and some international units with locations in Israel and formerly in Ukraine.

It is one of the largest Orthodox Jewish organizations in the United States. Its synagogues and their rabbis typically identify themselves with Modern Orthodox Judaism.

The OU was founded in 1898 by Rabbi Henry Pereira Mendes, and it serves today about 1,000 synagogues and congregations of varying sizes. The need for a national Jewish Orthodox rabbinical organization in the early twentieth century was recognized by a number of groups. The Union of Orthodox Rabbis was the most powerful rabbinical body at that time and many of its members saw great value in establishing the early Union of Orthodox Jewish Congregations of America.

Originally, the OU was formed by the same rabbis who created JTS, the Jewish Theological Seminary. JTS started as an Orthodox institution to combat the hegemony of the Reform movement. At the time, there was no Conservative movement by name, though there was a range of liberalism within Orthodox Jewry. Cracks between the OU and JTS first formed in 1902, shortly after Solomon Schechter's recruitment from Great Britain to head JTS. Schechter "liberalized" the institution and its approach to Torah study. Most of JTS's original founders, backers, and staff disavowed the changes, seeing it as headed toward the very philosophy JTS had been intended to hedge against. Exactly 100 days after Schechter's arrival, they formed a new Orthodox group, Agudath Harabonim, which refused to recognize the rabbinical credentials (Semicha) of those ordained at JTS, though Agudath explicitly wrote that the pre-Schechter graduates of JTS were fine rabbis and welcome.