James Powell Mattox (December 17, 1896 – October 12, 1973) was an American professional baseball player. He played as a catcher in Major League Baseball for the Pittsburgh Pirates in 1922 and 1923.
His brother, Cloy Mattox, played in three games for the Philadelphia Athletics in 1929. Another brother, Marv Mattox, was a teammate in college.
James played college football for the Washington and Lee Generals football team of Washington and Lee University. He was selected in 1919 to the College Football All-Southern Team. He made the field goal to upset Georgia Tech.
Mattox was later a catcher for the Pittsburgh Pirates from 1922 to 1923. He was then sold to the Wichita Falls club.