Shneur Zalman of Liadi was a rabbi and the founder and first Rebbe of Chabad, a branch of Hasidic Judaism. He wrote many works, and is best known for Shulchan Aruch HaRav, Tanya, and his Siddur Torah Or compiled according to the Nusach Ari.

A Rebbe or Admor is the spiritual leader in the Hasidic movement, and the personalities of its dynasties. The titles of Rebbe and Admor, which used to be a general honor title even before the beginning of the movement, became, over time, almost exclusively identified with its Tzadikim.