[dj_mc_merlin]

Paul McCartney himself: https://www.facebook.com/watch/?v=167778090799503

"I don't read music or write music, none of us do it in the Beatles. We did some good stuff though."

The 3 examples I listed are also probably the most well-known artists who have not studied theory, all 3 of them have said at various points in time that they can't read sheet music (and therefore definitely do not have a formal musical education). Funnily enough I _can_ read and play sheet music, and you do not see me drawing massive crowds..