What is the religion illuminati?

No, the Illuminati was never a religious organization. The 'Illuminati', was founded by Adam Weishaupt, a Bavarian writer and scholar, to oppose superstition, prejudice, to support women's education and gender equality, abuses of state power, and religious influence over public life. The organization eventually numbered about 2000 members throughout Europe. The name of the organization 'Illuminati', is the plural form for the Latin Word for 'enlightened ones'.

One of the goals of the Illuminati was the overthrow of an oppressive monarchy and the control of civil authorities by the Roman Catholic Church. They were very unsuccessful in their endeavor because that monarch, Karl Theodor, Duke of Bavaria and Prince-Elector of the Holy Roman Empire, successfully destroyed the organization and imprisoned their leadership, which ended the existence of the Illuminati.

The Illuminati that are rumored to be an organisation of social elite with far reaching global/political influence, therefor a band of stuffed suits, not a group ever to have been given any credence of religious affiliation; and never even widely conceived to truly exist.