Marie-Sophie Germain (Paris 1776 - 1831) was a self-taught mathematician, who made important contributions to number theory and elasticity theory. One of her most important works, Germain's Theorem, was an important step towards proving Fermat's last theorem. As a woman, she was unable to pursue a mathematical career in any academic institution, so she worked independently throughout her life. She autographed her research and studies as "M. Leblanc" to hide her identity.