Frederick John Rodney Warner (January 7, 1855 – February 13, 1886) was an American professional baseball third baseman. He played in Major League Baseball (MLB) from 1875 through 1884 for the Philadelphia Centennials, Philadelphia Athletics, Indianapolis Blues, Cleveland Blues, Philadelphia Quakers, and Brooklyn Atlantics. Warner died at the age of 31 in his hometown of Philadelphia, Pennsylvania, and is interred at The Woodlands Cemetery.