Halo is a military science fiction media franchise, originally developed by Bungie and currently managed and developed by 343 Industries, part of Microsoft's Xbox Game Studios.

The series launched in 2001 with the first-person shooter video game Halo: Combat Evolved and its tie-in novel, The Fall of Reach. The latest main game, Halo Infinite, was released in 2021. Combat Evolved started life as a real-time strategy game, then became a third-person shooter, and finally a first-person shooter releasing as an exclusive on Microsoft's new Xbox video game console after Bungie was acquired by the company. Bungie regained its independence in 2007, releasing additional Halo games through 2010. Microsoft established 343 Industries to direct the franchise going forward, and has produced games itself and in partnership with other studios.

Combat Evolved was a critical and commercial success, serving as the Xbox's "killer app" and cementing Microsoft as a major player in the video game console space. Its sequels expanded the franchise's commercial and critical success, and have sold more than 81 million copies worldwide. With more than $6 billion in franchise grosses, Halo is one of the highest-grossing media franchises of all time, spanning novels, graphic novels, comic books, short films, animated films, feature films, and other licensed products.