William Patrick Gannon (March 17, 1873 – April 26, 1927) was an American right fielder in Major League Baseball. He committed suicide in Fort Worth, Texas.
Gannon made his debut on September 9, 1901, at age 28. He appeared in 15 games. He collected 9 hits in 61 at-bats, scored 2 runs, and drew a base on balls 1 time. He hit no home runs. He had a batting average of .148 and a fielding percentage of 1.000.