Ordo Templi Orientis

Ordo Templi Orientis (O.T.O.) ('Order of the Temple of the East' or 'Order of Oriental Templars') is an international fraternal and religious organization founded at the beginning of the 20th century. English author and occultist Aleister Crowley has become the best-known member of the order.

Originally it was intended to be modelled after and associated with European Freemasonry, such as Masonic Templar organizations, but under the leadership of Aleister Crowley, O.T.O. was reorganized around the Law of Thelema as its central religious principle. This Law—expressed as "Do what thou wilt shall be the whole of the Law" and "Love is the law, love under will"—was promulgated in 1904 with the writing of The Book of the Law.

Similar to many secret societies, O.T.O. membership is based on an initiatory system with a series of degree ceremonies that use ritual drama to establish fraternal bonds and impart spiritual and philosophical teachings.

O.T.O. also includes the Ecclesia Gnostica Catholica (EGC) or Gnostic Catholic Church, which is the ecclesiastical arm of the Order. Its central rite, which is public, is called Liber XV, or the Gnostic Mass.

The early history of O.T.O. is difficult to trace reliably. It originated in Germany or Austria between 1895 and 1906. Its apparent founder was Carl Kellner (probably with the German spelling Karl), a wealthy Austrian industrialist, in 1895 (although nothing verifiable is known of the Order until 1904).

Theodor Reuss (1855–1923) collaborated with Kellner in creating O.T.O., and succeeded him as head of O.T.O. after Kellner's death. Under Reuss, charters were given to occult brotherhoods in France, Denmark, Switzerland, the U.S.A. and Austria. There were nine degrees, of which the first six were Masonic.

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