William Clarence "Cal" Hawk (October 20, 1847 – December 16, 1899) was an American professional baseball player in the 1870s. He played as a pitcher for the Oil City Senecas, the New Castle Neshannocks and the Bradford team. In 1873, he became the first pitcher to receive a stated salary, being paid $62 per month. He has been called "the first real professional hurler the game ever had." In 1899, the Sporting Life reported that he was "one of the first twirlers to pitch a curve ball, which in his time was considered a wonderful feat."