William Pearl Rhines (March 14, 1869 – January 30, 1922) was a professional baseball player. He was a pitcher over parts of 9 seasons (1890–1899) with the Cincinnati Reds, Louisville Colonels and Pittsburgh Pirates. He led the National League in ERA twice (1890 and 1896) while playing for Cincinnati. For his career, he compiled a 114–103 record in 249 appearances, with a 3.47 ERA and 743 strikeouts.
He was born and later died in Ridgway, Pennsylvania, at the age of 52. He was an alumnus of Bucknell University.