Menachem Mendel Schneersohn (or Menachem Mendel or Tzemach Tzedek) (1789 - 1866) was an Orthodox Judaism rabbi of the Chabad Lubavitch Hasidic Judaism movement that was based in the town of Lubavitch in present-day Belarus. He was the third Rebbe of the Chabad dynasty. Since 1940 the movement has had its headquarters in Brooklyn, New York in the United States with branches all over the world, forming an international movement.

Schneersohn was also known as the Tzemach Tzedek ("Righteous Sprout"), the name for a voluminous compendium of halakha (Jewish law) that he authored. He also authored Derech Mitzvotecha ("Way of Your Commandments"), a mystical exposition of halakha. He compiled major works of Rabbi Shneur Zalman of Liadi for publication, including the Siddur Mi'Kol Ha'Shanah, Likutei Torah and Torah Ohr.

The Tzemach Tzedek was unique among Chabad Rabbis because of his extraordinarily close relationship with members of other Jewish leaders. Rabbi Yechiel Michel Epstein spent six months under his tutelage, and told his children that he learned most of his mystical knowledge during that time. Rabbi Moses Sofer and Rabbi Akiva Eiger were also known to have a close correspondence with the Tzemach Tzedek.

Schneersohn was the grandson of the first Lubavitch Rebbe, Rabbi Shneur Zalman of Liadi, and became the son-in-law of the second Rebbe, Rabbi Dovber Schneersohn.

The seventh and last Lubavitch Rebbe, Rabbi Menachem Mendel Schneerson was fifth in a direct paternal line from this prior third Rebbe called "Menachem Mendel", and was named after him.

Rebbes of Lubavitch

• Chabad Lubavitch:

1. Shneur Zalman of Liadi (1745-1812)
2. Dovber Schneersohn (1773-1827)
3. Menachem Mendel Schneersohn (1789-1866)
4. Shmuel Schneersohn (1834-1882)
5. Sholom Dovber Schneersohn (1860-1920)
6. Joseph Isaac Schneersohn (1880-1950)
7. Menachem Mendel Schneerson (1902-1994)

Time-line of Lubavitcher rebbes