Perelman's Poincaré conjecture proof (2003)
Grigori Perelman posted three papers proving the Poincaré conjecture, the first Millennium Prize problem to be solved. His proof was verified by multiple teams of mathematicians within a few years.
Perelman was awarded the Millennium Prize in 2010 but declined it, along with the Fields Medal in 2006.
It remains the only Millennium Prize problem solved, showing both the difficulty of these problems and the verification process for major claims.
Perelman's proof shows what verified resolution of a Millennium Prize problem looks like, in contrast to the unverified 2026 Navier-Stokes claim.
