Microsoft today announced that the Xbox 360 exclusive game “Halo 3″ has officially become the biggest entertainment launch in history, garnering an estimated $170 million in sales in the United States alone in the first 24 hours. The Xbox 360 title beat previous records set by blockbuster theatrical releases like “Spider-man 3” and novels such as “Harry Potter and the Deathly Hallows.”

“Halo 3” is the conclusion to the epic trilogy and picks up where “Halo 2” left off, answering questions around the fates of the beloved protagonist Master Chief and his artificial intelligence sidekick Cortana as they struggle to save humankind from destruction at the hands of the alien coalition known as the Covenant. In addition to the rich storyline, “Halo 3” continues the franchise’s grand tradition of delivering innovative online multiplayer experiences via Xbox LIVE, the world’s largest social network on TV.

“Halo 3 has become a pop-culture phenomenon,” said Shane Kim, corporate vice president of Microsoft Game Studios. “Not only is “Halo 3” setting sales records, it’s also redefining entertainment.

Within the first 20 hours alone, we’ve seen more than a million Xbox LIVE members come online to play Halo 3 – that makes September 25 the most active Xbox LIVE gaming day in history.”

Retailers have also expressed their excitement about the launch of “Halo 3.”

Bob McKenzie, Senior Vice President of Merchandising for GameStop Corp commented that, “With consumer demand for Halo 3 and related products, we expect it to be the biggest video game title generator in GameStop’s history.”

“The initial demand we’ve seen for ‘Halo 3’ has been astounding, and the game is on track to become the number one gaming title of all time. ‘Halo 3’ is a genuine entertainment phenomenon and our customers have responded very enthusiastically to the release,” said Jill Hamburger, vice president of movies and games at Best Buy.

Developed by Bungie Studios, the “Halo” franchise is exclusive to the Xbox 360 video game and entertainment system and optimized for the Xbox LIVE online entertainment network. The more than 7 million Xbox LIVE users will get a continually evolving gaming experience with “Halo 3.” Its online multiplayer and cooperative gameplay for Xbox LIVE Gold users, the much-talked-about Saved Films feature that enables players to capture and save their favorite moments on their hard drives, and Forge, an innovative map editor that enables infinite customization options are just some of the new features to experience.

More than 10,000 retailers hosted Midnight Madness events to celebrate the launch of this third installment in the billion-dollar franchise. In New York, Seattle, Miami and Los Angeles, Microsoft and retail partners hosted marquee launch events that featured contests and appearances by local celebrities and professional athletes who are fanatical about the “Halo” franchise, including Ludacris and Zac Efron and Microsoft Chairman Bill Gates.

More than 1.7 million copies of “Halo 3” were preordered in the United States before a single store opened its doors at midnight, Sept. 25, making this the fasting pre-selling game in history, surpassing the previous record-setting pre-sales of “Halo 2.” Well beyond just a U.S. phenomenon, the launch of “Halo 3” was a worldwide celebration that released in 37 countries and available in 17 languages.