| Gerrer Rebbe | |
| Birth Name: | Yitzchak Meir Rotenberg-Alter |
| Main Work: | Chiddushei Harim |
| Predecessor: | none |
| Successor: | Chanokh Heynekh HaKohen Levin of Aleksander |
| Spouse: | Feigele Lipszyc |
| Children: | Avraham Mordechai Cyna Pesia Leah Hudes Esther |
| Dynasty: | Ger |
| Birth Date: | 1799 |
| Birth Place: | Magnuszew, West Galicia |
| Death Place: | Góra Kalwaria, Congress Poland |
| Place Of Burial: | Góra Kalwaria, Poland |
Yitzchak Meir Rotenberg-Alter (Yiddish: יצחק מאיר אלטער, Polish: Icchak Meir Rothenberg Alter, Hebrew: יצחק מאיר אלתר) (1799 – 10 March 1866), was the first Rebbe of the Ger Hasidic dynasty, which he founded in the town of Góra Kalwaria (known as "Ger" in Yiddish), Poland. He headed the Kupath Rabbi Meir Baal Haness Kollel Polen (Poland) Varsha (Warsaw) (Hebrew). He was also known as The Chiddushei HaRim for his Torah writings, and was sometimes fondly called Reb Itche Meir (Yiddish) by his followers.
Alter was born in Magnuszew, Austrian Poland, in late 1799. He came from a very distinguished family of rabbis, among the most prominent in Germany and Poland. He was a descendant of Rashi and of the Tosafist, Rabbi Meir ben Baruch of Rothenburg.
He married Feigele Lipszyc, daughter of Moshe 'Halfon' Lipszyc, in 1811, and settled in Warsaw. They had fourteen children, according to most published sources, most of whom died in infancy.
Alter became known as a Talmudic gaon. At first, he was close to the rebbes of Kozhnitz, however after some years, he was drawn to Rebbe Simcha Bunim of Peshischa, whose close adherent he became. After the demise of Simcha Bunim, Alter became a disciple of Rabbi Menachem Mendel of Kotzk, also known as the Kotzker Rebbe, who was famous for his acerbic wit and Talmudic brilliance. He was soon followed by a large number of Simcha Bunim's followers. Alter and the Kotzker Rebbe eventually became brothers-in-law, when the latter married Chaya Lipszyc, the sister of Alter's wife Feigele.
In 1830, he was forced to change his name to Alter because of his support towards the Poles during the November Uprising.
Alter was temporarily succeeded as the Rebbe of the Ger hasidim by his colleague and disciple, Rabbi Chanoch Henoch of Aleksander.
One of his sons, Avraham Mordechai, and three daughters, Cyna Pesia, Leah Hudes, and Esther, survived to adulthood and married. However, by the time of Alter's death on 23 Adar 5626 (1866), only one child (Esther) remained alive.
Rabbi Alter is still well known for his talmudic commentary, though he wrote on many other areas. Extant published works are: