William Leopold Doak (January 28, 1891 – November 26, 1954) was an American Major League Baseball pitcher who played for three teams between 1912 and 1929.

He led the National League in earned run average in 1914, and he won 20 games in the 1920 season.

[1] The St. Louis Cardinals purchased Doak's contract in the summer of 1913, and he spent the majority of his career with that team.

Even though Doak played with many unremarkable teams, he is among the Cardinals' top 10 in eight pitching categories; his 32 shutouts rank second behind Bob Gibson.

In 1920, he suggested to Rawlings that a web should be laced between the first finger and thumb, saying it would create a natural pocket.