The Revival of the Religious Sciences

The Revival of the Religious Sciences (Arabic: إِحْيَاء عُلُوم ٱلدِّين, romanized: Iḥyāʾ ʿUlūm al-Dīn) is a 12th-century book written by the Muslim scholar al-Ghazali. The book was composed in Arabic by Ghazali on his spiritual crises that stemmed from his appointment as the head of the Nizamiyya University in Baghdad, which led to his eventual disappearance from the Muslim world for over 10 years. It is widely considered to be the most influential book in Islamic history after the Quran and canonical hadith collections.

It is regarded as one of his chief works and a classic introduction to the pious Muslim's path to God. It originally spanned 40 volumes and dealt with Islamic concepts and practices, demonstrating how these might be formed the foundation of reflective religious life, thereby attaining the higher stages of Sufism. Some consider Kimiyā-ye Sa'ādat (Alchemy of Happiness) as a rewrite of this work, which is a common misconception. Kimyā-ye Sa'ādat is shorter than this book; however, Ghazali said that he wrote the former to reflect the nature of the latter and a few of his other theological writings.