The Keyblade War is an event in the Kingdom Hearts series of video games. The Keyblade War actually takes place long before the events of the games, but plays a major role in shaping the games.
The Keyblade War is presented as backstory in the Kingdom Hearts games. It was a conflict over control of the Kingdom Hearts that led to the creation of Keyblades. The war centered around the X-Blade, a keyblade that is the means of controlling Kingdom Hearts. Master Xehanort, one of the primary antagonists of the series, is directly influenced by the events of the Keyblade War.