Al-Jafr (Arabic: الجفر‎; also romanized as Jafr or Ḥỵr) is a book written by Al-Jafr, a Persian, in the Islamic year 676. It was also one of the most important books for the Islamic religion.

Al-Jafr was one of the greatest Muslim philosophers and religious thinkers of the early Islamic era. His works have been collected into two main categories, the "Logic" and the "Utterances", with several hundred pages in between.

In "Al-Jafr", he presents his famous "Paradox of the Cave" as well as his ideas on a number of subjects, including epistemology, metaphysics, ethics, theology, and the Quran.

This book has been translated into a number of languages, including English, Urdu, and Persian.