Kotsk (Kotzk) is the name of a Hasidic dynasty founded by Rebbe Menachem Mendel Morgenstern, known as the Kotzker Rebbe.
Kotsk is the Yiddish name of Kock, a town in present-day Poland.
The first Rebbe of Ger, Rabbi Yitzchak Meir Alter, known for his work as the Chidushei Harim, was a preeminent disciple of the Kotzker Rebbe. Following the Kotzker's death most of the Kotzker Hasidim formed the nucleus of the Ger dynasty.
The Kotzker Hasidim were known for their critical thinking and for a controversial way of expressing themselves.
Rebbe Menachem Mendl Morgensztern of Kotsk (originally of Tomashov) (1787–1859), the Alter Kotsker Rebbe
Rebbe Dovid Morgensztern of Kotsk (1809–1873), son of Rebbe Menachem Mendl
Rebbe Yaakov Yehoshua Morgensztern of Kotsk (1836–1907), son of Rebbe Dovid
Rebbe Chayim Yisroel Morgensztern of Pilov (1840–1905), author of Shloim Yerusholayim, son of Rebbe Dovid
Rebbe Tsvi Hersh Morgensztern of Łuków (1858–1920), author of Ateres Tsvi, son of Rebbe Chayim Yisroel
Rebbe Moshe Mordechai Morgensztern of Pilov (1862–1929), author of Medrash Moshe, son of Rebbe Chayim Yisroel
Rebbe Yitschok Zelig Morgensztern of Sokolow(1866–1939), son of Rebbe Chayim Yisroel
Rebbe Yaakov Menachem Mendl Morgensztern of Wengrow (1887–1939), son of Rebbe Yitschok Zelig
Rabbi Shlomo Morgenstern, London & Chicago, the last Kotsker Rebbe Son of Rebbe Yaakov Menachem Mendel of Wengrow
Rabbi Avraham Morgenstern, Chicago & Miami, Son of Rebbe Yaakov Menachem Mendle of Wengrow
Rebbe Tsvi Hersh Morgensztern of Lomaz, Łomazy District (1852–1926), son of Rebbe Dovid
Rebbe Yaakov Arye Morgensztern of Wyszków (born 1878), son of Rebbe Tsvi Hersh of Lomaz
Rabbi Shalom Morgenstern, Scarsdale, New York (8th generation descendant of the Kotzker Rebbe)
Rabbi Mendle Meir Morgenstern, Kotzker Rebbe currently residing in Jerusalem. Published Amud Haemes and other Seforim of the dynasty
