|This article relies on references to primary sources. (April 2008)|
In Scientology, Operating Thetan (OT) is a spiritual state above Clear. L. Ron Hubbard, science fiction writer and creator of Scientology, defined it as "knowing and willing cause over life, thought, matter, energy, space and time (MEST)". According to religious scholar J. Gordon Melton, "It's basically a variation of the Gnostic myth about souls falling into matter and the encumbrances that come with that".
Scientology doctrine defines OT as the "highest state there is". The OT is able to "control or operate thought, life, matter, energy, space, and time" whether he or she has a body, mind or not. The state of Operating Thetan is represented by a symbol consisting of the letters OT with the T inside the O and each of the points of the T ending at the O's circumference, evoking not only the level's initials but also the medieval O-T map representing the known world and, metaphorically, the entirety of the observable universe, over which a fully developed OT allegedly has immediate control.
In March 2008, the Church of Scientology's Operating Thetan documents were leaked on WikiLeaks. The Church of Scientology claimed their hosting is a copyright violation implying that the collection is Church doctrine.
Following its rise to prominence, a growing number of former Scientologists have made public allegations that the church encourages its members to complete very expensive courses and expect wonderful results; when the improvements fail to be realized, further courses are then promoted to facilitate the anticipated changes. Criticism stems from a pattern of perpetuity wherein members continue to pay increasing amounts for these courses, while some even put their families into debt chasing the elusive life-changing results under the stewardship of the "church".
OT I 
"This Solo-audited level is the first step a Clear takes toward full OT abilities, and that first step is a fresh causative OT viewpoint of the MEST universe and other beings." The cost to 'upgrade' to this level is $2,750.
OT II 
"By confronting hidden areas of one's existence on the whole track, vast amounts of energy and attention are released. Those on this Solo-audited level experience a resurgence of self-determinism and native ability. OT II unlocks the aberrative factors on the whole track that have allowed the thetan to lose his innate freedom and ability and one achieves the ability to confront the whole track." The cost to 'upgrade' to this level is $5,225.
OT III: The Wall of Fire 
"This Solo-audited level goes through what is called the "Wall of Fire" that surrounds a previously impenetrable whole track mystery. What prevents a being from being himself? This level answers that question. Once complete, a being is free of the whole track overwhelm that has trapped him. Here he confronts and eradicates the fourth dynamic engram that has plagued this universe for millennia."The cost to 'upgrade' to this level is $8,910.
Church dogma regards OT III as a dangerous process which can lead to pneumonia, to lack of sleep or even to death if not run correctly. In Church of Scientology of California v. Kaufman, it was noted that the defendant had been required to sign a waiver to the effect that "the Scientology Organization, its branches and members, and L. Ron Hubbard are not responsible for anything that might happen to my body or mind on OT III".
OT IV: OT Drug Rundown 
"This level handles the hidden problems and stops in a being's universe caused by the effects of drugs and poisons on the whole track. This is the final polish that rids one of any last vestige of the effects of drugs on the spirit. Ministered at Advanced Organizations or Flag. Approximately 12½ to 25 hours."
OT V: New Era Dianetics for OTs 
"The Second Wall of Fire consists of 26 separate rundowns and has been described as dealing with "living lightning, the very stuff of life itself." This level addresses the last aspects of one's case that can prevent him from achieving total freedom on all dynamics. An audited level ministered at Advanced Organizations or Flag. Approximately 50 hours."
OT VI: Hubbard Solo New Era Dianetics for OTs (Solo NOTs) Auditing Course 
"The training one receives before starting to solo audit on New OT VII is so powerful that it actually constitutes an entire OT level. On Solo NOTs one is dealing with complexities intended to crush one's true power and abilities as a thetan. Solo NOTs auditors acquire a wide range of auditing skills to handle the vast phenomena that can occur on OT VIII. Approximately 3–4 weeks with the new Solo Auditor Course done."
OT VII: Hubbard Solo New Era Dianetics for OTs Auditing 
"On New OT VII one solo audits at home daily. This is a lengthy level, requiring a considerable amount of time to complete. It is the final pre-OT level, and culminates in attainment of the state of CAUSE OVER LIFE."
OT VIII: Truth Revealed 
"This Solo-audited level addresses the primary cause of amnesia on the whole track and lets one see the truth of his own existence. This is the first actual OT level and brings about a resurgence of power and native abilities for the being himself. This may be done at the Flag Ship Service Organization only."
Unreleased levels 
- OT IX: Orders of Magnitude
- OT X: Character
- OT XI: Operating
- OT XII: Future
- OT XIII: New Section XIII OT
- OT XIV: New Section XIV OT
- OT XV: New Section XV OT
- At some point one is to eventually reach the state of Cleared Theta Clear, a spiritual state which Hubbard describes this way:
"A thetan who is completely rehabilitated and can do everything a thetan should do, such as move MEST and control others from a distance, or create his own universe." 
See also 
- The State of Operating Thetan (Church of Scientology)
- Verini, James (2005-06-28). "Missionary Man: Tom Cruise and the Church of Scientology". Salon.com. Spiegel Online. Retrieved 2008-10-26.
- Technical Dictionary of Dianetics and Scientology; L. Ron Hubbard; Bridge Publications; ISBN 0-88404-037-2
- The Official Scientology and Dianetics Glossary definition of pre-OT levels; accessed 2008-02-03 (mirror)
- www.whatisscientology.org, Grade chart of scientology courses, training and processing
- wikinews:Church of Scientology's 'Operating Thetan' documents leaked online
- Metz, Cade (8 April 2008). "Scientology threatens Wikileaks with injunction". The Register. Retrieved 2008-12-09.
- Atack, Jon  A Piece of Blue Sky, Carol Pub. Group, Chap 3, ISBN 0-8184-0499-X http://www.xenu.net/archive/books/apobs/bs1-3.htm
- What is Scientology compiled by the staff of Church of Scientology International. c1998 published Bridge Publications Inc. ISBN 1-57318-078-5 pg. 840-841
- "Chapter 7 OT -- Through the Wall of Fire and Beyond". The OT Levels. Retrieved 12 February 2013.
- Church of Scientology of California v. Kaufman,  F.S.R. 591 per Goff J - in the Chancery Division of the High Court
- Hubbard, Scientology 8-8008, pg 114 (1st ed), pg. 151 (1990 ed.), pg. 207 (2007 ed.)
- "Operating Thetan levels". A description of the OT levels. Church of Scientology.
- "What is meant by Operating Thetan or OT?". An answer to a commonly asked question. Church of Scientology.
- "OT Hatting Courses". Special courses and lectures related to OT levels. Church of Scientology. Archived from the original on 10 January. 2008.
- "OT Level Successes". Success stories related to the OT levels. Church of Scientology. Archived from the original on 8 October. 2007.
- "The State of Operating Thetan". A description. Church of Scientology.
- Summary of Operating Thetan levels 1-8
- The Fishman Affidavit (Karin Spaink)
- Operating Thetan Summary and Analysis (Michael Robinson)
- The NOTs Scholars Home Page (Scientology) (David S. Touretzky)
- Ariane JACKSON answers about OT8 (Ariane Jackson)
- The complete Fishman papers
- Church of Scientology collected Operating Thetan documents (Wikileaks)