Robert Calvin Hubbard (October 31, 1900 – October 17, 1977) was a professional American football player and later an umpire in Major League Baseball. A member of three major sports halls of fame, Hubbard is credited as being one of the inventors of the football position of linebacker. To date Hubbard is the only person to be enshrined in both the Pro Football Hall of Fame and the Baseball Hall of Fame. He is also a member of the College Football Hall of Fame.