Halo 2 is a science fiction first-person shooter video game developed by Bungie Studios. Released for the Xbox game console on November 9, 2004, the game is the sequel to Halo: Combat Evolved. After its initial release, Halo 2 was the most popular video game on Xbox Live, holding that rank until the release of Gears of War for the Xbox 360 nearly two years later. By June 20, 2006, more than 500 million games of Halo 2 had been played and more than 710 million hours have been spent playing it on Xbox Live; by May 9, 2007, this number had risen to more than five million unique players on Xbox Live. As of May 9, 2006, 8 million units of the game have been sold worldwide, with 6.3 million of those units being sold in the United States alone. As of September 25, 2007, Halo 2 is the fifth best-selling video game in the US and is the best-selling first-generation Xbox game worldwide.

In the game, humans, who have developed faster-than-light travel and colonized hundreds of worlds, have been engaged in a war against a collective of genocidal alien races, the Covenant. The player assumes the roles of Master Chief and the Arbiter, and fights enemies on foot or with a collection of alien and human vehicles.