The Illuminati was a secret society started by Adam Weishaupt to overthrow the new ideals of rationalism, religious freedom and universal human rights propagated by Catholic Church during the 18th century. The group didn’t necessarily oppose religion – they just believed it should be kept separate from governance. There’s no evidence that the Illuminati exists today.
ScienceSwitch 
A better question might be, Is the Catholic Church (for) real?
(Full disclosure: the questioner is an ex-Catholic.)
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