Halo 5: Guardians will be released for Xbox One on October 27th. The date comes via a new live-action trailer that you can watch above; it won't tell you much about the game itself, but it appears that things aren't too rosy between Master Chief and new protagonist Jameson Locke. (As a commenter notes below, there's another version of the trailer which turns the tables. We've included that too.)
For more on how Halo 5 is mixing up the series, you can read our impressions of the game's multiplayer here. And, if you need to catch up on your convoluted sci-fi lore in the seven months before Guardians drops, Halo: The Master Chief Collection is out now on Xbox One and includes the first four Halo games.