Grigori Yakovlevich Perelman (Russian: Григорий Яковлевич Перельман), born 13 June 1966 in Leningrad, USSR (now St. Petersburg, Russia), sometimes known as Grisha Perelman, is a Russian mathematician who has made landmark contributions to Riemannian geometry and geometric topology. In particular, it appears that he has proved Thurston’s geometrization conjecture. If so, this solves in the affirmative the famous Poincaré conjecture, posed in 1904 and regarded as one of the most important and difficult open problems in mathematics.
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“. The Fields Medal is widely considered to be the top honor a mathematician can receive. However, he declined to accept the award or appear at the congress.