Tzadik/Zadik/Sadiq (Hebrew: צדיק‎ "righteous one", pl. Tzadikim צדיקים ṣadiqim) is a title given to personalities in Jewish tradition considered righteous, such as Biblical figures and later spiritual masters. The root of the word ṣadiq, is ṣ-d-q (צדק Tzedek), which means "justice" or "righteousness", also the root of Tzedakah (Charity, lit. "righteousness"). The feminine term for a righteous person is Tzadeikas.

The term Tzadik "righteous", and its associated meanings, developed in Rabbinic thought from its Talmudic contrast with Hasid ("Pious" honorific), to its exploration in Ethical literature, and its esoteric spiritualisation in Kabbalah. In Hasidic Judaism, the institution of the Tzadik assumed central importance, combining former elite mysticism with social movement for the first time. Adapting former Kabbalistic theosophical terminology, Hasidic thought internalised mystical experience, emphasising deveikut attachment to its Rebbe leadership, who embody and channel the Divine flow of blessing to the world.