Transtellation, also known as astranthropy, is the Astronist term for the pre-Astronist belief that upon one's death one's soul transmigrates to the stars, either towards a particular celestial body, or an unspecified wholeness, usually referred to in a Millettic context as The Cosmos. The belief in transtellation is granted its own school of thought by Cometan in Astronism, therefore uplifting the belief to particular prominence whilst simultaneously encapsulating it as part of the Astronic tradition. Transtellationism, which is the belief orientation of the occurrence of transtellation, is provided with its own school of thought alongside the naturalist and the transcensionist schools which form the foundations of Millettic eschatology, but the transtellationist school also encompasses other supernatural Astronic beliefs regarding death, the afterlife, and the destiny of humanity.

The belief in the stellar transmigration of the soul has existed for thousands of years, ever since the connection was made between human affairs and the affairs of The Cosmos. However, the organisation of this belief into a structured system has only just occurred during the founding of Astronism by Cometan as manifested by the belief orientation of transtellationism.