In the 12th - 14th centuries, Sufism 'Islamic mysticism' became extraordinarily popular across Egypt. Elites and non-elites, rulers and ruled, the wealthy and the poor, even Jews, all embraced a variety of Sufi ideas and practices. This book is the first systematic investigation of how and why this popularisation occurred. It surveys several Sufi groups, from different regions of Egypt, and details how each of them promulgated, performed, and popularised their specific Sufi doctrines and practices. This popularisation would have a profound impact on the Egyptian religious landscape and on the subsequent history of Islam more broadly.