Igrot Kodesh (literally "Holy Epistles" but more commonly known as "Letters of the Rebbe") is a collection of correspondence and responses of the seventh Rebbe of Chabad-Lubavitch, Menachem Mendel Schneerson.
It is modeled after Igrot Kodesh Maharayatz which are the letters of the sixth Rebbe of Lubavitch, Yosef Yitzchok Schneersohn. The topics considered in these letters comprise of many realms of discussion, and numerous disciplines of human pursuit. Its purview encompassing philosophy (be it Talmudic, Halachic, Hasidic, mystical or other), scientific matters, global events, counsel in private issues, schooling, and social/communal proceedings.
There is a prevalent practice among certain, particularly messianic, members of Chabad-Lubavitch to use the Igrot in bibliomancy.