Iḥya Uloom (translation  The Revival of Knowledge Arabic: إحياء علوم ) is an 11th-century book written by Abu Ḥamid Muḥammad ibn Muḥammad al-Ghazali.The book was composed in Arabic and was based on personal religious experience. It is regarded as one of his chief works and a classic introduction to the pious muslim's way to God. Originally spanning over 40 volumes, it deals with the principles and practices of Islam and demonstrates how these can be made the basis of a reflective religious life, thereby attaining the higher stages of Sufism. Some consider Kimiya-ye Saadat as a rewrite of this work, which is a common misconception. Kimya-ye Saadat is shorter than this, however Ghazali said that he wrote the former to reflect the nature of the latter and a few of his other theological writings.

The book is divided into four parts,
each containing ten books. It explains the doctrines and practices of Islam and showed how these can be made the basis of a profound devotional life, leading to the higher stages of Sufism or mysticism.