The Church of Science is a fictional religion from Isaac Asimov's Foundation series. It is first mentioned in Part III of Foundation, "The Mayors", and makes its last appearance in Part V, "The Merchant Princes".
In the novel Foundation, the Foundation, a large colony of scientists on the planet Terminus, find themselves cut off from their supporters in the Galactic Empire and threatened by the newly independent neighboring Kingdom of Anacreon, which covets their possession of scientific knowledge and nuclear power. The leader of Terminus, Mayor Salvor Hardin, visits three other nearby kingdoms and convinces their leaders that allowing Anacreon to conquer Terminus would make that kingdom powerful enough to conquer them in turn. The three other kingdoms force Anacreon to back down.
Hardin goes on to offer scientific and medical assistance to all four kingdoms, reasoning that this will make them less likely to join together for a combined assault on Terminus. The barbarized inhabitants of the four kingdoms believe that the Foundation's technicians are magicians. Being unable to make these people understand the difference between magic and science, the technicians finally give up and allow themselves to be worshipped as holy men. Back on Terminus, Hardin accepts the situation, and organizes the Foundation's technical assistance program as a religion. The technicians are organized into a priesthood, and the Foundation's ambassador to each kingdom becomes the High Priest, with Hardin himself assuming the role of Chief Primate of the whole religion.
The resulting religion is never given a formal name in the novel, but it is referred to several times as the "religion of science", hence the name "Scientism".
In addition to the technician-priests (an atomic priesthood that controls the technology of nuclear power) from Terminus who travel to the worlds of the Four Kingdoms, the church also recruits priests from among the native populations of those worlds. They travel to a Temple School in Terminus City, where they are taught the operation (though not the theoretical underpinnings) of the Foundation's technology, along with more traditional religious instruction in church dogma, theology and ethics. Any novitiate priest at the Temple School who is bright enough to see through the mystical surface to the scientific principles underneath remains on Terminus to become a research student. The rest return to the Four Kingdoms to form part of the priesthood.