Paul Henry Castner (February 16, 1897 – March 3, 1986) was a professional baseball pitcher.

Castner played for the Notre Dame Fighting Irish football team as a fullback from 1919 to 1922, under Knute Rockne.

He appeared in six games in Major League Baseball for the Chicago White Sox in 1923, all in relief.

In 10 innings pitched, Castner gave up 14 hits and 5 walks without striking out a batter.

This biographical article relating to an American baseball pitcher born in the 1890s is a stub.