Scientology founder L. Ron Hubbard routinely referred to "space opera" in his teachings, drawing from science-fiction and weaving it into his origins of human history. In his writings, wherein thetans (roughly comparable to the concept of a human soul) were reincarnated periodically over quadrillions of years, retaining memories of prior lives, to which Hubbard attributed complex narratives about life throughout the universe. The most controversial of these myths is the story of Xenu, to whom Hubbard attributed responsibility for many of the world's problems.

Some space opera doctrines of Scientology are only provided by the church to experienced members, who church leaders maintain are the only ones able to correctly understand them. Several former members of the church have exposed these secret documents, leading to lengthy court battles with the church, which failed to keep the secret. Critics of the church have noted that some of the narratives are scientifically impossible, and have thus assailed the church as untrustworthy for teaching them. The space opera teachings have also been satirized in popular culture. Scholars of religion have described the space opera narratives as a creation myth designed to encourage reverence of Hubbard as a supreme messenger. Several academics have drawn attention to the similarity of the space opera myths to themes of the 1950s Cold War culture in which they were constructed.

(Although this article regularly refers to Xenu, Hubbard in some of his lectures and writings actually uses the name Xemu and even spells it out).

L. Ron Hubbard created a set of beliefs that he represented as a form of therapy, which he named Dianetics. He promoted it as a scientific, not religious, teaching. The system has no scientific basis and is a type of pseudoscience. Until the early 1950s, Hubbard had a negative view of organized religions, but thereafter discussed spiritual topics. In these teachings, he claimed to identify subconscious memories of past events, which he called "engrams", as causes of human dissatisfaction. By 1950, he had begun to ponder past lives, believing that they could be recalled; he attempted to use these recollections to develop a comprehensive narrative of the universe. He founded the Church of Scientology in 1953, advancing his beliefs as religious doctrines. The church was distinct from Dianetics-based groups but incorporated some of their views. Hubbard saw Dianetics as focused on the physical body but viewed Scientology as a way to address spiritual matters.

In Hubbard's efforts to shift from a psychotherapeutic to a spiritual program, he introduced the concept of thetans: a set of godlike, non-corporeal entities capable of creating and shaping universes, later trapped in the MEST universe and confined, by reincarnation, to physical bodies. Hugh Urban of Ohio State University states that these teachings bear similarities to Gnosticism, although he doubts that Hubbard was well versed in Gnostic thought.

In the 1950s, as Hubbard's followers recalled their past lives, he recorded many details of these recollections. With this as his source, he constructed an intricate history of the universe, identified as "space opera". Although Hubbard believed that he had developed a comprehensive history, Urban cites the isolated and incomplete record of the statements, wherein Hubbard identified a thetan universe, separate from the material universe, created by its inhabitants. The material universe, in Hubbard's view, began when other universes created by thetans collided, from which they entered the material universe in six invasion groups roughly 60 trillion years ago. Hubbard also described a series of events, called the "incidents", which divorced the thetans from their self-knowledge, but maintained that thetans could regain their former divinity, and referred to thetans that freed themselves from the material world as "operating thetans".

Hubbard located his first 'incident' four quadrillion years ago, in which a thetan encountered 'loud cracks and brightness' and then observed a cherub and chariot before experiencing total darkness. In Scientology, this is known as "Incident 1". Another important event in Scientology's chronology of the universe occurred on a space city known as Arslycus, the inhabitants of whom brought about an incident when capturing thetans.

The most controversial portion of Scientology's space opera is the myth of Xenu, known as "Incident 2", in which Hubbard described a group of 76 planets, orbiting stars visible from Earth, organized in a Galactic Confederacy c. 75 million years ago, ruled by the dictator Xenu. The confederacy having become overpopulated, Xenu sent several billion of his citizens onto DC 8 planes to the planet Teegeeack (Earth), ostensibly for tax audition. There, hydrogen bombs were detonated inside volcanoes, killing the exiles, whose thetans were brainwashed on Hawaii and the Canary Islands, introducing various myths, such as the myth of Jesus, to conceal the thetans' origins. Eventually, officers of the Galactic Confederacy launched a rebellion against Xenu, which continued for six years before capturing him and placing him in an electrified prison in the center of a mountain. Hubbard taught that the thetans brainwashed by Xenu's forces remained on Earth, where the "body thetans", attached to human psyches, contribute to human problems; and that individuals could be freed from these brainwashed thetans and thus attain a type of salvation.