From Wikipedia: Master Chief is a fictional character and the main protagonist of the Halo universe, created by video game developer Bungie. Master Chief is a playable character in the trilogy of science fiction first-person shooter video games Halo: Combat Evolved, Halo 2, and Halo 3. Outside of video games, the character appears in the novels Halo: The Fall of Reach, Halo: The Flood, Halo: First Strike, and Halo: Uprising, and has cameos in Halo media including Halo: Ghosts of Onyx, The Halo Graphic Novel and Halo Legends. He is voiced by Chicago disc jockey Steve Downes in the video games in which he appears.
Master Chief is one of the most visible symbols of the Halo series and the video game universe. Originally designed by Bungie artists including Marcus Lehto, Rob McLees, and Shi Kai Wang, the character is a towering and faceless cybernetically enhanced supersoldier; he is never seen without his green-colored armor or helmet. Downes built his personification of the Chief off a character description which called for a Clint Eastwood-type character of few words.