Mordecai Menahem Kaplan (June 11, 1881, Švenčionys – November 8, 1983, New York City) was a rabbi and essayist and the founder of Reconstructionist Judaism. Kaplan was born in Švenčionys, Lithuania and was ordained as a rabbi at Jewish Theological Seminary of America (JTS) in New York City in 1902. Kaplan began his career as an Orthodox rabbi at Congregation Kehilath Jeshurun, a synagogue in New York. He helped to create the Young Israel movement of Modern Orthodox Judaism with Rabbi Israel Friedlander, was a leader in creating the Jewish community center concept, and helped found the Society for the Advancement of Judaism.