The organisers of Live 8 have announced the performers' names in alphabetical order "because so many stars were taking part" it was impossible to choose a headline act.
In London's Hyde Park, those performing include Mariah Carey, Coldplay, Dido, Keane, Sir Elton John, Annie Lennox, Madonna, Muse, the Scissor Sisters, Sir Paul McCartney, Joss Stone, Stereophonics, Sting, Snoop, Robbie Williams, U2 and REM.
In Philadelphia, acts performing will include Will Smith, the Dave Matthews Band, Bon Jovi, Stevie Wonder, Puff Daddy and Jay-Z.
Among artists scheduled for Berlin are A-Ha, Crosby, Stills and Nash, Lauryn Hill and Brian Wilson.
The concert in Rome will feature musicians including Faith Hill and Duran Duran.
In Paris, Jamiroquai, Craig David, Youssou N’Dour and Yannick Noah will be among those taking part.
Geldof said the concert was not going to be "gloomy and doomy" and was "not for charity but for political justice".
He said organisers had “scrambled like crazy to put this together”, adding: “I think we’re almost there.”
He said: “The continent in those 20 years … has gone into economic decline by a factor of 25%. The result of that is we see people dying on TV screens every night. This is to finally, as much as as we can, put a stop to that.”
He added: “It seemed to me that we could gather again, not for charity but for political justice.”