Grigori Yakovlevich Perelman is a Russian Jewish mathematician, who has made landmark contributions to Riemannian geometry and geometric topology. In particular, he proved Thurston’s geometrization conjecture.

In August 2006, Perelman was awarded the Fields Medal for “his contributions to geometry and his revolutionary insights into the analytical and geometric structure of the Ricci flow”. Perelman declined to accept the award or to appear at the congress. On 22 December 2006, the journal Science recognized Perelman’s proof of the Poincaré conjecture as the scientific “Breakthrough of the Year”, the first such recognition in the area of mathematics. He has since ceased working on mathematics. On 18 March 2010, it was announced that he had met the criteria to receive the first Clay Millennium Prize Problems awardof US $1,000,000 for resolution of the Poincaré conjecture but on July 1, 2010 he turned down this one million dollar prize saying that he believes his contribution in proving the Poincare conjecture was no greater than that of U.S. mathematician Richard Hamilton, who first suggested a program for the solution.