The Tzadikim Nistarim (Hebrew: צַדִיקִים נִסתָּרים, "hidden righteous ones") or Lamed Vav Tzadikim (Hebrew: ל"ו צַדִיקִים,x"36 righteous ones"), often abbreviated to Lamed Vav(niks), refers to 36 righteous people, a notion rooted within the more mystical dimensions of Judaism. The singular form is Tzadik Nistar (Hebrew: צַדִיק נִסתָר).
The source is the Talmud itself, explained as follows:
As a mystical concept, the number 36 is even more intriguing. It is said that at all times there are 36 special people in the world, and that were it not for them, all of them, if even one of them was missing, the world would come to an end. The two Hebrew letters for 36 are the lamed, which is 30, and the vav, which is 6. Therefore, these 36 are referred to as the Lamed-Vav Tzadikim. This widely-held belief, this most unusual Jewish concept is based on a Talmudic statement to the effect that in every generation 36 righteous "greet the Shekhinah", the Divine Presence (Tractate Sanhedrin 97b; Tractate Sukkah 45b).
Mystical Hasidic Judaism as well as other segments of Judaism believe that there exist 36 righteous people whose role in life is to justify the purpose of humankind in the eyes of God. Jewish tradition holds that their identities are unknown to each other and that, if one of them comes to a realization of their true purpose, they would never admit it: