The Millennium Prize Problems are seven problems in mathematics that were stated by the Clay Mathematics Institute in 2000. The problems are:

Riemann hypothesis, and
A correct solution to any of the problems results in a US $1M prize (sometimes called a Millennium Prize) being awarded by the institute. The only solved problem is the Poincaré conjecture, which was solved by Grigori Perelman in 2003.
Will another Millennium Prize Problem be solved before 2028?
This question will resolve in the positive if the Clay Institute accepts a solution to one of the six remaining outstanding problems before the end of 2027. The prize does not have to have been awarded or accepted by this time, as long as it is generally accepted that the Institute recognises the proof.