That would be Adam Weishaupt, a German philosopher.
In 1773, Weishaupt was made the chair of canon law at the University of Ingolstadt, a university in Bavaria that was largely influenced by the Roman Catholic Church. Before his appointment, the position had been occupied by priests for 90 years. Two years later he was made dean of the university at the age of 27—and many of the priests at the university weren't happy with the young hotshot who was gaining power. Jesuits and Weishaupt fought over the church's "intolerance" and "bigotry," and this led Weishaupt to conclude that a secret group of like-minded thinkers would be the only way to overthrow the status quo. So, he wanted to be a Freemason, of course. Only problem is that he didn't have the money to pay the admission fee (and he also concluded in the end that the Freemasons weren't secret enough). Making his own society was the next best alternative.
The Order of the Illuminati would grow from five members to thousands, thanks to recruitment from Freemason lodges and other European countries. Because they became so popular, staying hidden wasn't so easy. Secret societies were made illegal and punishable by death a few years after Karl Theodor became ruler of Bavaria in 1777. This was the end of the Order of the Illuminati (so we think). Weishaupt moved to Gotha, Germany, where he died in exile.