George Silas Haddock (December 25, 1866 – April 18, 1926), nicknamed Gentleman George, was a 19th-century Major League Baseball pitcher. He played from 1888 to 1894 in the Players' League, American Association and National League. Haddock played right field for the Washington Nationals against the Cleveland Spiders, on September 4, 1889. He relieved George Keefe, who worked four innings as the Nationals' starting pitcher.