Perelman was awarded the Fields Medal in 2006 for this accomplishment, but he declined to accept the award.
First Clay Mathematics Institute Millennium Prize Announced Today
Prize for Resolution of the Poincaré Conjecture Awarded to Dr. Grigoriy Perelman
The Clay Mathematics Institute (CMI) announces today that Dr. Grigoriy Perelman of St. Petersburg, Russia, is the recipient of the Millennium Prize for resolution of the Poincaré conjecture. The citation for the award reads:
The Clay Mathematics Institute hereby awards the Millennium Prize for resolution of the Poincaré conjecture to Grigoriy Perelman.
It is well-known that the Clay prize comes with $1 million in prize money. As you might guess, Twitter is abuzz with the news and speculation as to whether Perelman will accept the money.
The most reliable information I have seen are two tweets by Alex Bellos, who wrote:
Oh, if you would like to know what the Poincaré conjecture is, check out this video…