Halo 3 is now available on PC

Now, Halo 3 is available for PC on Steam, the Microsoft Store and through Xbox Game Pass, both as a standalone title and through Halo: The Master Chief Collection.  

So far, PC’s edition of Halo: The Master Chief Collection has received versions of Halo: Reach, Halo: Combat Evolved and Halo 2: Anniversary, each of which supports 60FPS framerates, or higher (in some cases), and support for higher quality visuals than the game’s original Xbox 360 and Xbox One iterations. These PC versions also ship with support for both gamepads and mouse/keyboard inputs. 

Halo ODST and Halo 4 remain as the only games in the Master Chief Collection that are yet to release on PC, leaving Halo 5 as the only game in the franchise to lack a confirmed PC release. With Halo: Infinite coming later this year, we should expect Microsoft to reveal its plans for Halo 4 and ODST soon.    
Halo 3 and Halo: The Master Chief Collection are available on PC through Steam and the Microsoft Store.