What is the most least popular and unknown religion in the world?

Answer 1

Religions that don't have significant financial influence also do not have much prominence. In other words if the product is not marketed effectively it would not be well-known and it will not attract much patrons.

Answer 2

That's probably one I never heard about. Seriously, it depends what you want to accept as a "religion". There are probably several people who have some belief that is shared by nobody else, so that would make millions of religions with only one follower each. You can go even further and invent some religion that NOBODY believes in, so potentially you have an infinity of religions with zero followers.