Sufism, the mystical or aesthetic doctrine in Islam, has occupied a very specific place in the Islamic tradition, with its own history, literature and devotional practices. Its development began in the seventh century, almost immediately after the early conquests, and spread throughout the Islamic world. The Cambridge Companion to Sufism traces its evolution from the formative period to the present, addressing specific themes along the way within the context of the times. In section discussing the early period, the devotional practices of the earliest Sufis are considered. The section on the medieval period, when Sufism was at its height, examines Sufi doctrines, different forms of mysticism and the antinomian expressions of Sufism. The section on the modern period explains the controversies that surrounded Sufism, the changes that took place in the colonial period and how Sufism transformed into a transnational movement in the twentieth century. This inimitable volume sheds light on a multifaceted and alternative aspect of Islamic history and religion.