Two years have passed since the last King of Fighters tournament and nobody has seen Kyo Kusanagi or Iori Yagami since they defeated Orochi at the climax of the 1997 tournament, but out of the blue, new invitations are sent out to many characters, inviting them to a brand new tournament, though this competition is more of a secretive affair than the ones in '96 and '97.

"The King of Fighters '99: Millennium Battle" is the sixth game in The King of Fighters series by SNK. Unlike in previous games of the series, there are four characters per team instead of three, with the fourth serving as a "Striker", a fighter whose function is only to enter a match, attack the opponent and leave without replacing their teammates. In total, there are seven teams, each containing four characters, four Team Edit characters and a boss.