The Society for the Advancement of Judaism, also known as SAJ, is a Reconstructionist synagogue and Jewish organization in New York City, on Manhattan's Upper West Side. Founded in 1922 by Mordecai M. Kaplan, the rabbi who founded of Reconstructionist Judaism, the synagogue is affiliated with the Reconstructionist movement.

The current rabbi is Lauren Grabelle Herrmann, who succeeded Michael Strassfeld on 1 July 2015.

Moshe Nathanson, composer of Hava Nagilah, was Cantor of the SAJ during Kaplan's tenure.

The first American Bat Mitzvah was held at the Society for the Advancement of Judaism on Saturday morning, March 18, 1922, for Judith Kaplan, daughter of Rabbi Mordecai Kaplan.