Real World eventsEdit
- February 26: Halo Wars was released in Japan and Australia.
- February 27: Halo Wars was released in the PAL Region.
- April 9: The first Mythic Map Pack was released.
- April 15: Issue 4 of the Halo: Uprising comic book series was released.
- May 19: The Strategic Options Pack for Halo Wars was released, including the game modes Reinforcements, Tug of War and Keep Away.
- June 1:
- July 21: Historic Battle Map Pack, the first map pack for Halo Wars, was released.
- July 22: Issue 1 of the Halo: Helljumper series of comics was released.
- July 24: The Announcement Trailer for Halo Legends was released.
- August 26: Issue 2 of Halo: Helljumper was released.
- September 7: The Life was released.
- September 22:
- September 23: Issue 3 of Halo: Helljumper was released.
- October 19: The Halo Encyclopedia was released.
- October 28: Issue 4 of Halo: Helljumper was released.
- November 5: Halo Waypoint was released.
- November 7: The Babysitter short film shown on Halo Waypoint.
- November 21: The Duel short film was shown on Halo Waypoint.
- November 24: Halo: Evolutions - Essential Tales of the Halo Universe is released.
- November 25: Issue 5 of Halo: Helljumper was released.
- December 5: The Package Part One short film was shown on Halo Waypoint.
- December 12:
- The Package Part Two was shown on Halo Waypoint.
- Halo: Reach Video Games Awards Trailer was aired live on the Spike TV Video Game Awards 2009.
- December 23: Issue 1 of the Halo: Blood Line comic series was released.
- Halo: Chronicles was officially canceled.