https://wccftech.com/halo-3-pc-july-14/

Halo 3 PC will be joining Halo: The Master Chief Collection next week on July 14, Microsoft and 343 Industries have announced.

The news was announced via the official Halo Twitter account just now. Aside from becoming available through the Microsoft Store and Steam, the game will also be a playable through Xbox Game Pass as part of The Master Chief Collection.