Leona Lewis and the Sugababes are just some of the stars getting ready for one of the biggest ever birthday parties.
They're going to be singing at a special concert to celebrate the 90th birthday of the former South African president, Nelson Mandela.
He's one of the most famous men in the world, and spent years in jail campaigning for the rights of black people in South Africa.
Many artists have also flown in from the country to perform at the show.
It's thought they'll be joined by Amy Winehouse, who has recently been in hospital, being treated for lung disease.
Since Mr Mandela retired from politics nine years ago, he has campaigned around the world for peace and an end to poverty.
As well as celebrating his birthday, the concert will raise funds for charity.