It's the UK art world's best known award and often controversial.
Not surprising when you think past winners have included a painting made with elephant dung and a pickled sheep!
Some critics say it's turned into 'a national joke.'
But the exhibition showing the shortlisted entries attracts 120,000 visitors a year.
A spokesman says Madonna was asked to present the prize because she's always been interested in the visual arts.
The singer will hand over the £20,000 prize to the winning entry on December 9 at the Tate Modern art gallery in London.