Stephanie Louise Kwolek (July 31, 1923 – June 18, 2014) was an American chemist, whose career at the DuPont company spanned over forty years. She is best known for inventing the first of a family of synthetic fibers of exceptional strength and stiffness: poly-paraphenylene terephthalamide—better known as Kevlar. For her discovery, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement.