Rebbetzin (Yiddish: רביצין) or Rabbanit (Hebrew: רַבָּנִית) is the title used for the wife of a rabbi, typically from the Orthodox, or Haredi, and Hasidic Jewish groups.
The Yiddish word has a trilingual etymology: Hebrew rebbə "master", plus the Slavic feminine suffix -itsa and the German feminine suffix -in.
In many Chassidic courts, Rebbetzins are considered to be spiritual counselors, and give blessings. In circles such as the Hassidic dynasty of Belz, the girls schools are run by the rebbetzin. There are also several recorded instances of female rebbes, who while technically rebbetzins, were full-fledged rebbes in their own right. One such famous case is the Maiden of Ludmir.
The rabbi's wife plays an important community role, especially in small communities. In many ways, she is called on to be as knowledgeable as the rabbi in the realm of woman's observances: in this manner, for something that does not require a psak (ruling), she can be approached when a woman does not feel comfortable approaching the rabbi, or where the rabbi maybe should not be approached. For instance, the rebbetzin may often be the "mikvah lady" and help with more mundane questions regarding the laws of niddah. Part of it, certainly, is that she always has the rabbi's ear, and that she would know if the question needs to be asked, in order to get a psak.
When a rabbi is a "pulpit rabbi," (versus a teacher or a "lay rabbi") his wife becomes something of a first lady of the community and performs social tasks and "outreach" roles, freeing her husband to attend to rabbinical duties.
With the growth of independent scholarship among Orthodox women, some women have informally received the title on their own merit, irrespective of their husbands.