Sir Michael Francis Atiyah, OM, FRS (b. April 22, 1929) is a British mathematician, wiely considered one of the greatest geometers of the 20th century. His path-breaking work with Isadore Singer led to the proof of the Atiyah-Singer index theorem in the 1960s, a result that has helped to pave the way for the development of several branches of mathematics since that time.