- Pawel Czernek enters active service with the UNSC Marine Corps.
- Deep Winter died.
- February 20: The Spartan-III's of Gamma Company undergo augmentations on the UNSC Hopeful.
- November 24: The Mjolnir Powered Assault Armor/Mark V enters service.
- December 22: The Car & Pilot Magazine releases its December 2551 Edition. This includes a review of the new 2553 edition of the Civilian "Hog".