oldest American federation of Jewish congregations, which, since its founding (1873) in Cincinnati, Ohio, has sponsored many programs to strengthen Jewish congregations and promote Jewish education on every level.

The union was organized by rabbi Isaac Mayer Wise (Wise, Isaac Mayer) for the immediate purpose of establishing and supporting a seminary for the training of American-born rabbis, who, Wise felt, were the key to the future of Judaism in the United States. Two years later the union established Hebrew Union College, the first successful rabbinic seminary in the United States. In 1950 this college merged with the Jewish Institute of Religion of New York, founded in 1922 by Rabbi Stephen S. Wise. Both institutions were long-time centres of Reform Judaism and are still supported by the union.

The union organized five auxiliary groups: the National Federation of Temple Sisterhoods (1913), of Temple Brotherhoods (1923), of Temple Youth (1939), and of Temple Secretaries (1943) and the National Association of Temple Educators (1955). Each group operates independently within the union and promotes those activities that best suit it.

The union has sponsored or cosponsored religious schools, teacher seminars, a correspondence school, student study groups, and leadership training courses, often in cooperation with other groups.

The union, now numbering some 600 Reform congregations (including several in Canada), is affiliated with the World Union for Progressive (Reform) Judaism and maintains headquarters in New York City.