William Paul Macdonald, Jr. (March 28, 1929 – May 4, 1991) was an American professional baseball player, a right-handed pitcher who appeared in 36 Major League games for the 1950 and 1953 Pittsburgh Pirates.

Born in Alameda, California, he stood 5 feet 10 inches (1.78 m) tall and weighed 170 pounds (77 kg) as an active player.

After winning 15 games during the latter season for the Flint Arrows of the Class A Central League, Macdonald was declared a free agent by Commissioner of Baseball Happy Chandler on October 27, 1948; three months later, he signed with the New Orleans Pelicans, the Pirate affiliate in the Double-A Southern Association.

[1] When he returned to baseball in 1953, he pitched ineffectively for the Pirates during the season's early weeks and spent much of the campaign with the Hollywood Stars of the Open-Classification Pacific Coast League.

All told, in 1601⁄3 Major League innings pitched, Macdonald gave up 150 hits and 96 bases on balls; he struck out 64.