William Harpin (Bill) Mellor (June 6, 1874 – November 5, 1940) was a Major League Baseball first baseman. Mellor played for the Baltimore Orioles in 1902. In 10 career games, he had 13 hits in 36 at-bats, with 5 RBIs. He batted and threw right-handed. Mellor attended both Brown University and the University of Virginia.