Toldos Aharon is a devout, insular, fervently anti-Zionist Hasidic group. The group is characterized by extreme conservatism and a desire to preserve the life of the old Yishuv in Jerusalem, in sharp opposition to Zionism, in a strict Haredi way of life, in a special style of clothing, and in an emphasis on prayer at a moderate pace and with enthusiasm. Headquartered in Jerusalem's Mea Shearim neighborhood, it also has significant numbers in Ramat Beit Shemesh, and New York City, and additional members in Tiberias and in Harish. The sect has about 1,800 households. Toldos Aharon is a split-off from Shomer Emunim. It is led by its Rebbe, Dovid Kohn.

Hasidism, sometimes spelled Chassidism, and also known as Hasidic Judaism, is a religious movement within Judaism that arose as a spiritual revival movement in Poland and contemporary Western Ukraine, during the 18th century, and spread rapidly throughout Eastern Europe. Today, most of those affiliated with the movement, known as hassidim, reside in Israel and in the United States.