Milletto-Montserratian philosophy, Montserratian Millettism, and also known as Montserratian Astronism, as part of the larger British Millettism denomination, refers to the presence of The Philosophy of Millettism in Montserrat under management and philosophical jurisdiction of The Institution of The Philosophy of Millettism for Montserrat, which is under authority of The Institution of the Philosophy of Millettism for the United Kingdom of Great Britain and Northern Ireland, a national subsidiary for the worldwide Institution of The Philosophy of Millettism.
The Institution of the Philosophy of Millettism for Montserrat oversees the construction and maintenance of observatories and planetariums throughout its jurisdiction. Montserrat is split into three parishes and holds one Grand Observatory, which is also the only Millettarian observatory in this British Overseas Territory.
This national branch of The Institution of The Philosophy of Millettism manages the official representation and depiction of Astronism throughout this territory, including efforts to protect the identity of the philosophy with the intention of further disseminating it throughout the territory. It is The Institution alone that is granted the status of proprietor to the philosophy in this territory as any other organisations or institutions proclaiming such a role are deemed as unauthorised proprietors and are therefore considered as part of the anti-Institutionist movement.