(1452-1519. Leonardo was born just before the War of the Roses, and was about 40 when Columbus sailed to the Americas. He died not long after the start of the Reformation.)
I bet you've heard of Leonardo. Perhaps you've been to see the Mona Lisa, maybe you've read the Da Vinci code (I haven't done either - I've been put off by the queues at the Louvre and the first few pages of the Da Vinci Code. I hope it gets better as you get into it). You hopefully remember the Teenage Mutant Ninja Turtles, though.
But beyond the whole art thing - and very little of Leonardo's art survives - he was also an engineer and a mathematician. Plus, he was left-handed like me!
He may not have broken much ground as a mathematician - he wrote a book on the theory of mechanics and some pretty cool geometry - but he did say this:
"No human investigation can be called real science if it cannot be demonstrated mathematically."
And people remember him for a helicopter that didn't work and a painting of a woman with a wonky smile. Tsh.
I've picked Leonardo as a Mathematical Ninja because he really epitomises my idea of what a mathematician should be: fascinated by the world around him, and curious to know how it works. He studied maths because it was useful, not because it was cool1 and applied it to what he was interested in.
Who would you nominate as a Mathematical Ninja?