Charles "Cy" Rigler (May 16, 1882 – December 21, 1935) was an American umpire in Major League Baseball who worked in the National League from 1906 to 1935. His total of 4,144 games ranked fourth in major league history when he retired, and his 2,468 games as a plate umpire still place him third behind his NL contemporaries Bill Klem (3,543) and Hank O'Day (2,710). Rigler is tied with O'Day for the second most World Series as an umpire (10), trailing only Klem's 18. Rigler has also been credited with instituting the practice of using arm signals when calling balls and strikes.