What was the first Halo game released for the Xbox One?

Halo: The Master Chief Collection was the first Halo game released for the Xbox One.

The collection launched in 2014 and brought together anniversary or remastered versions of major games centered on Master Chief. Its original package included Halo: Combat Evolved Anniversary, Halo 2: Anniversary, Halo 3, and Halo 4, along with multiplayer content associated with those titles.

The collection was designed as a large retrospective package rather than a wholly new numbered campaign. It therefore arrived before Halo 5: Guardians, which became the next mainline original game on Xbox One.

A frequent source of confusion is the distinction between a collection and an individual game. Halo 5 is often named because it was the first new mainline Halo title developed specifically for that console generation, but the collection was released earlier and is the correct answer to the broader question about the first Halo game on Xbox One.