L. Ron Hubbard, the founder of Scientology, announced the story of Xenu in a taped lecture sent to all Scientologists.

Lafayette Ronald Hubbard was an American author and the founder of Scientology. A prolific writer of pulp science fiction and fantasy novels in his early career, in 1950 he authored the pseudoscientific book Dianetics: The Modern Science of Mental Health and established organizations to promote and practice Dianetics techniques. Hubbard created Scientology in 1952 after losing the intellectual rights to his literature on Dianetics in bankruptcy. He would lead the Church of Scientology – variously described as a cult, a new religious movement, or a business – until his death in 1986.

Scientology is a set of beliefs and practices invented by the American author L. Ron Hubbard, and an associated movement. It is variously defined as a scam, a business, a cult, or a religion. Hubbard initially developed a set of pseudoscientific ideas that he represented as a form of therapy, which he called Dianetics. An organization that he established in 1950 to promote it went bankrupt, and his ideas were rejected as nonsense by the scientific community. He then recast his ideas as a religion, likely for tax purposes and to avoid prosecution, and renamed them Scientology. In 1953, he founded the Church of Scientology which, by one 2014 estimate, has around 30,000 members.

Xenu, also called Xemu, is a figure in the Church of Scientology's secret "Advanced Technology", an esoteric teaching held sacred by adherents. According to the "Technology", Xenu was the extraterrestrial ruler of a "Galactic Confederacy" who brought billions of his people to Earth in a DC-8-like spacecraft 75 million years ago, stacked them around volcanoes, and killed them with hydrogen bombs. Official Scientology scriptures hold that the thetans of these aliens adhere to humans, causing spiritual harm.