Master Chief Petty Officer John-117, commonly called the Master Chief, is a fictional character and the main protagonist of the trilogy of science fiction first-person shooter video games Halo: Combat Evolved, Halo 2, and Halo 3. Master Chief also appears in the novels Halo: The Fall of Reach, Halo: The Flood, Halo: First Strike, and Halo: Uprising, and has cameos in Halo: Ghosts of Onyx and the Halo Graphic Novel. He is voiced by Chicago disc jockey Steve Downes.

Master Chief Petty Officer John-117, commonly called the Master Chief, is a fictional character and the main protagonist of the trilogy of science fiction first-person shooter video games Halo: Combat Evolved, Halo 2, and Halo 3. Master Chief also appears in the novels Halo: The Fall of Reach, Halo: The Flood, Halo: First Strike, and Halo: Uprising, and has cameos in Halo: Ghosts of Onyx and the Halo Graphic Novel. He is voiced by Chicago disc jockey Steve Downes.