William "Bill" Grey (Biru Gurei) is a fictional character in Nintendo's Star Fox franchise. He is an ace pilot in the Cornerian Army that serves out of Katina. He wears a Green Ace Commander Helmet on his head. He was good friends with Fox McCloud, who convinced him to join the Cornerian Flight Academy with him some years ago. When Fox left the Academy to avenge his father's death at the hands of Andross, Bill went on to become an ace pilot and was given command of both the Husky and Bulldog squadrons. He helped defend Katina during the Lylat Wars and the Anglar invasion.
If the mission is accomplished on Katina, Bill will help with opening the warp gates in Sector X or help with fighting monsters on Solar, depending on the route Fox takes. A similar role is played by Katt Monroe.