Haredi or Charedi/Chareidi Judaism is the most conservative form of Orthodox Judaism, often referred to as ultra-Orthodox. A follower of Haredi Judaism is called a Haredi (Haredim in the plural).

Haredi Jews, like other Orthodox Jews, consider their belief system and religious practices to extend in an unbroken chain back to Moses and the giving of the Torah on Mount Sinai. As a result, they regard non-Orthodox, and to an extent Modern Orthodox, streams of Judaism to be deviations from authentic Judaism. Haredi Judaism comprises a diversity of spiritual and cultural orientations, generally divided into Hasidic and Lithuanian-Yeshiva streams from Eastern Europe, and Oriental Sephardic Haredim. Its historical rejection of Jewish secularism distinguishes it from Western European-derived Modern Orthodox Judaism.

The word Ḥaredi (חֲרֵדִי), which originally was simply the Hebrew translation of Orthodox, is derived from charada, which in this context (Orthodoxy) is interpreted as "one who trembles in awe of God"; the word itself means fear or anxiety.

As of 2011, there are approximately 1.3 million Haredi Jews. The Haredi Jewish population is growing very rapidly, doubling every 17 to 20 years.