On August 22, 2006, the ICM awarded Perelman the Fields Medal for his work on the Ricci flow, but Perelman refused the medal.

[...]

The Clay Mathematics Institute, having included the Poincaré conjecture in their well-known Millennium Prize Problem list, offered Perelman their prize of US$1 million in 2010 for the conjecture's resolution. He declined the award, saying that Hamilton's contribution had been equal to his own

https://arxiv.org/abs/math/0211159

https://en.wikipedia.org/wiki/Grigori_Perelman

https://en.wikipedia.org/wiki/Richard_S._Hamilton

https://en.wikipedia.org/wiki/Ricci_flow

https://en.wikipedia.org/wiki/Millennium_Prize_Problems

Note: the possible second Millennium Prize Problem solution (Navier–Stokes, possibly solved recently) has still not yet been verified by CMI.

On August 22, 2006, the ICM awarded Perelman the Fields Medal for his work on the Ricci flow, but Perelman refused the medal.

[...]

The Clay Mathematics Institute, having included the Poincaré conjecture in their well-known Millennium Prize Problem list, offered Perelman their prize of US$1 million in 2010 for the conjecture's resolution. He declined the award, saying that Hamilton's contribution had been equal to his own

https://arxiv.org/abs/math/0211159

https://en.wikipedia.org/wiki/Grigori_Perelman

https://en.wikipedia.org/wiki/Richard_S._Hamilton

https://en.wikipedia.org/wiki/Ricci_flow

https://en.wikipedia.org/wiki/Millennium_Prize_Problems

Note: the possible second Millennium Prize Problem solution (Navier–Stokes, possibly solved recently) has still not yet been verified by CMI.