Pierre de Fermat (1601 - 1665)

Pierre de Fermat, born 17th August 1601, laid the foundations of Probability Theory, did a lot of work on Number Theory, and is famous today for his "Fermat's Last Theorem" because he died before giving a proof.

In the margin of his copy of Diophantus' Arithmetica, Fermat wrote:

"To divide a cube into two other cubes, a fourth power or in general any power whatever into two powers of the same denomination above the second is impossible, and I have assuredly found an admirable proof of this, but the margin is too narrow to contain it."

In today's language:

"No integral values of x, y, z can be found to satisfy the equation  xⁿ + yⁿ = zⁿ   if n be an integer greater than 2"

It was not until 300 years later in 1994 that Fermat's Last Theorem was proved by Andrew Wiles.

You can read more about Fermat here: 

http://www-history.mcs.st-and.ac.uk/Mathematicians/Fermat.html

and many other mathematicians at the Mac Tutor site here:  

http://www-history.mcs.st-andrews.ac.uk/index.html