Halo 3 is a first-person shooter video game developed by Bungie Studios exclusively for the Xbox 360. The game is the third title in the Halo series and concludes the story arc that began in Halo: Combat Evolved and continued in Halo 2.

Halo 3 holds the record for the highest grossing opening day in entertainment history, bringing in US$170 million in its first 24 hours, going on to gross US$300 million in its first week. More than one million people played Halo 3 on Xbox Live in the first twenty hours. As of January 3, 2008, Halo 3 has sold 8.1 million copies, and is the best-selling video game of 2007 in the U.S.

Halo 3's story centers on the interstellar war between 26th century humanity, led by the United Nations Space Command, and a collection of alien races known as the Covenant. The player assumes the role of the Master Chief, a cybernetically enhanced supersoldier, as he wages war in defense of humanity, assisted by human Marines as well as allied alien Elites led by the Arbiter.