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 קופת רמבעה"ן כולל פולין ורשה / וארשא‎).

He was also known as The Chiddushei HaRim (החדושי הרי"ם‎) for his Torah writings, and was sometimes fondly called Reb Itche Meir (Yiddish) by his followers.

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.

One of his sons, Avraham Mordechai, and three daughters, Cyna Pesia, Leah Hudes, and Esther, survived to adulthood and married.