Although there are a number of conspiracy theories proposing all sorts of evidence connecting Leonardo Da Vinci to Freemasonry and other (real or imagined) secret societies, there is nothing in his (extensively studied) notebooks to indicate their veracity, nor is there anything in his other work to indicate he was a member of a secret society. In fact, Leonardo Da Vinci was famously lazy, disorganized, and almost always underemployed: not the kind of person who you would want to participate in a secret society.

I wrote more in-depth about Leonardo Da Vinci's life and his role in Italian history here.