Not to be confused with Astronism.

Astrocism, also known as Astronic mysticism, astronomical mysticism, siderealism, or the cosmic mystical tradition is a dispositional discipline of Astronism exploring all spiritual and mystical aspects of the religion.

As derived from the term astrosis meaning "knowledge of astronomical mysteries", Astrocism was the first Cometanic belief orientation and concept to be introduced and developed post-omnidoxically. Therefore, neither of these terms were ever mentioned in the Omnidoxy directly, although indirect references to this tradition of mysticism in Astronism were made in the founding text, particularly within the Monodoxy.

Despite this, Astrocism remains one of the most prominent foundational beliefs to Astronism and lead to the development of a tradition of mysticism within Astronism. Astrocism can be described as the Astronist version of Gnosticism, a 2nd-century heretical movement within the Christian Church.

The fundamental principle of Astrocism is that The Cosmos holds a plethora of astronomical, spiritual, and intellectual mysteries which are to be explored as part of the existential purpose of humanity, thus existing in parallel to beliefs such as transcensionism and the Humanic Exploration of The Cosmos. Astrocism has a close relationship with cosmic alchemy as the purpose of this practice is to discover the astronomical elixir through the proximation of our relationship to The Cosmos, known as cosmosis.

Astrocism holds a variety of forms within Astronism, namely including the tradition of alchemy within Astronism known as cosmic alchemy which proclaims its beliefs and practices to be the superior way of achieving corporeal cosmosis.