The Classical World Chess Championship 2004 was held from September 25, 2004, to October 18, 2004, in Brissago, Switzerland. Vladimir Kramnik, the defending champion, played Peter Leko, the challenger, in a fourteen-game match.

The World Chess Championship 2006 was a match between Classical World Chess Champion Vladimir Kramnik and FIDE World Chess Champion Veselin Topalov. The title of World Chess Champion had been split for 13 years. This match, played between September 23 and October 13, 2006, in Elista, Kalmykia, Russia, was to reunite the two World Chess Champion titles and produce an undisputed World Champion.