George Zettlein (July 12, 1844 – May 22, 1905) was an American professional baseball pitcher. He played six seasons in Major League Baseball from 1871 to 1876 for the Chicago White Stockings, Troy Haymakers, Brooklyn Eckfords, Philadelphia White Stockings of the National Association (NA), and the Philadelphia Athletics (1860–1876) of the National League. Zettlein had an overpowering fastball and was regarded as one of the best pitchers of his era.