This is the first comprehensive reference work to cover the entire domain of Gnosis and Western Esotericism from the period of Late Antiquity to the present. Containing around 400 articles by over 180 international specialists, it provides critical overviews discussing the nature and historical development of all its important currents and manifestations, from Gnosticism and Hermetism to Astrology, Alchemy and Magic, from the Hermetic Tradition of the Renaissance to Rosicrucianism and Christian Theosophy, and from Freemasonry and Illuminism to 19th-century Occultism and the contemporary New Age movement. Furthermore it contains articles about the life and work of all the major personalities in the history of Gnosis and Western Esotericism, discussing their ideas, significance, and historical influence.