Bungie, the developer of the hugely popular Halo series, is to part company with owner Microsoft.
In a statement, the two firms said they would "forge a new long-term partnership" based around new games.
The move will surprise many in the games industry, despite rumours about a split in recent weeks.
Bungie is now a privately held company in which Microsoft holds a minority stake. Recent release Halo 3 racked up $300m in its first week on sale.
The Halo series has sold more than 18 million copies worldwide since the first game was launched in 2001. Halo 3 has become the fastest selling game of all time following its launch on 25 September, with more than three million copies already sold.
Bungie now has a long-term publishing agreement with Microsoft Game Studios for future Halo titles.
Harold Ryan, studio head at Bungie, said Microsoft's platforms would remain the firm's "primary focus" but the move opens up the possibility of the studio developing for other consoles.
"Bungie is like a shark. We have to keep moving to survive," said Jason Jones, Bungie founder and partner.
Shane Kim, corporate vice president of Microsoft Game Studios, said the company was "supporting Bungie's desire to return to its independent roots".
He said Microsoft would to invest in Halo entertainment property with Bungie and other partners, such as Peter Jackson, on "a new interactive series set in the Halo universe".
"We look forward to great success with Bungie as our long-term relationship continues to evolve through Halo-related titles and new IP (intellectual property) created by Bungie," he added.
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Bungie Parts From Microsoft
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