Millennium Prize Problems are 7 seemingly impossible unsolved Mathematics problems that were revealed in 2000 and rewarded a $1 million prize to anyone who could solve one. In 2003, Gregori Perelman became the first (and so far only) person to solve one. He turned down the prize money.
The Interfax news agency quoted Perelman as saying he believed the prize was unfair. Perelman told Interfax he considered his contribution to solving the Poincaré conjecture no greater than that of another mathematician.