William Joseph Kelly (May 1, 1886 – June 3, 1940) was an American professional baseball player. He played in parts of four seasons in Major League Baseball for the St. Louis Cardinals and Pittsburgh Pirates from through . He also managed the minor league Port Huron Saints in 1922. Kelly was born in Baltimore, Maryland and died of lung cancer in Detroit, Michigan at the age of 54.
In a brief 4 year, 104 game major league career, Kelly compiled a .290 batting average with 32 runs, 1 home run and 21 RBI.