- Not to be confused are UFO religions or ancient astronaut theories that posit that historical religious scripture or mythology was inspired by visits from extraterrestrials.
- "Exotheism" is a fictional denomination in the Vampire: The Requiem role-playing game.
The term "exotheology" was coined in the 1960s or early 1970s for the examination of theological issues as they pertain to extraterrestrial intelligence. It is primarily concerned with either conjecture about possible theological beliefs that extraterrestrials might have, or how our own theologies have been or will be influenced by evidence of and/or interaction with extraterrestrials. One of the main themes of Exotheology is applying the concept of extraterrestrials who are sentient, and more to the point, endowed with a soul, as a thought experiment to the examination of a given theology, mostly Christian theology, occasionally also Jewish theology.
A Christian writer early to address the question was C. S. Lewis (1898–1963) who in a 1950s article in the Christian Herald contemplated the possibility of the Son of God incarnating in other, extraterrestrial, worlds, or else that God could devise an entirely distinct plan of salvation for extraterrestrial communities from the one applicable to humans.
Lutheran apologist Ted Peters (2003) asserts that the questions raised by the possibility of extraterrestrial life are by no means new to Christian theology and by no means pose, as asserted by other authors, a threat for Christian dogma. Peters points out that medieval theology had frequently considered the question of "what if God had created many worlds?", as early as the discussion of the Antipodes by the Church Fathers.
The Catholic Vatican theologian Corrado Balducci often discussed the question in Italian popular media, and in 2001 published a statement UFOs and Extraterrestrials - A Problem for the Church? In a 2008 statement, José Gabriel Funes, head of the Vatican Observatory, said "Just as there is a multiplicity of creatures on earth, there can be other beings, even intelligent, created by God. This is not in contrast with our faith because we can't put limits on God's creative freedom".
Rabbi Aryeh Kaplan, who was also a physicist, was inclined toward the belief in extraterrestrial life, citing various classic Jewish authorities. Among them are the medieval philosopher Rabbi Chasdai Crescas (Ohr Hashem 4:2) and 18th century kabbalist Rabbi Pinchas Eliyahu Horowitz (Sefer HaBris). After presenting his sources, Rabbi Kaplan remarks, "We therefore find the basic thesis of the Sefer HaBris supported by a number of clear-cut statements by our Sages. There may even be other forms of intelligent life in the universe, but such life forms do not have free will, and therefore do not have moral responsibility"—at least in the same sense as human beings.
Rabbi Norman Lamm, former chancellor of Yeshiva University, has also written on this subject, asserting that if the existence of extraterrestrial life should be confirmed, religious scholars must revise previous assumptions to the contrary. He, too, does not rule out this possibility from an Orthodox Jewish point of view.
Smaller denominations also have similar treatments in passing in their key writings: Christian Science and the Course in Miracles treat extraterrestrials as effectively brother spiritual beings in a non-absolute physical experience, the founder of the former writing, "The universe of Spirit is peopled with spiritual beings,...", and Emmanuel Swedenborg wrote, "Anyone with a sound intellect can know from many considerations that there are numerous worlds with people on them. Rational thought leads to the conclusion that massive bodies such as the planets, some of which are larger than our own earth, are not empty masses created merely to wander aimlessly around the sun, and shine with their feeble light on one planet. No, they must have a much greater purpose than that. . . . What would one planet be to God, who is infinite, and for whom thousands, or even tens of thousands of planets, all full of inhabitants, would be such a trifling matter as to be almost nothing?"  While other Protestant denominations have tended to be somewhat terracentric much as Roman Catholicism did until more recent time, receptivity to the idea of extraterrestrial civilizations likely depends on the degree of associated biblical literalism. Those of more fundamentalist leanings as interviewed occasionally on UFO- and paranormal-themed radio shows like Coast to Coast AM often try to fit extraterrestrial beings into the mold of demons or Nephilim, lacking much better category in which to place them, whereas schools of less literal persuasion would be more open to alternative perspectives. These would include either fundamental reexamination of traditional assumptions, some reconsideration of extraterrestrials as in some sense angels, or at least wider interpretations possible in the saying ascribed to Jesus of Nazareth, "And other sheep I have which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.", which while probably quite presumptuous-sounding in the very large cosmic perspective could potentially lend itself to a reading in some more impersonal sense as well better befitting the larger magnitude of exotheology.
Depending on the suras cited, the Quran of Islam appears to leave open the door to the idea of extraterrestrials, as in 27:65, situated similarly on a par with humans subject to a divine judgment leading toward a heaven or hell as reward for the deeds of one's life. 
- An early attestation is the title "A Jewish Exotheology" in Norman Lamm, Faith and Doubt: Studies in Traditional Jewish Thought, Ktav Pub. House, 1971, p. 107.
- "Dabbling in Exotheology". Time (magazine). 1978-04-24. Retrieved 2007-05-10.
- Vatican scientist says belief in God and aliens is OK Reuters, May 14, 2008 Pope's astronomer insists alien life 'would be part of God's creation', The Independent, 15 May 2008.
- [Aryeh Kaplan. "On Extraterrestrial Life."] The Aryeh Kaplan Reader, Artscroll/Mesorah Publications.
- "A Jewish Exotheology," published as Chapter 5 in Norman Lamm, Faith and doubt: studies in traditional Jewish thought, Ktav Pub. House, 1971, p. 107.
- Eddy, Mary Baker, Science and Health with Key to the Scriptures, p. 264:32.
- Woofenden, Lee and Annette (2014-12-08). ""Aliens vs. Advent: Swedenborg’s 1758 Book on Extraterrestrial Life"". Retrieved 2016-02-05.
- The Christian Bible (King James Version), John 10:16
- "Aliens and UFOs in the Noble Quran". 2001-03-06. Retrieved 2016-02-05.
- "Islam and Extraterrestrial Life". 2015-08-18. Retrieved 2016-02-05.
- Thomas F. O'Meara, O.P. "Christian Theology and Extraterrestrial Intelligent Life." Theological Studies 60 (1999): 3-30.
- Ted Peters, Science, theology, and ethics, Ashgate science and religion series, 2003, ISBN 978-0-7546-0825-7, chapter 6: "Exotheology: Speculations on Extraterrestrial Life"