William Porter "Spike" Shannon (February 7, 1875 – May 16, 1940) was a professional baseball player and umpire. Shannon was an outfielder over parts of five seasons (1904–1908) with the St. Louis Cardinals, New York Giants and Pittsburgh Pirates. He was the National League leader in runs scored in 1907, when he scored 104 runs for the Giants. For his career, he compiled a .259 batting average, 183 runs batted in, 383 runs scored, and 145 stolen bases. After his playing career, he was an umpire in the Federal League during 1914 and 1915 for a total of 177 games.