William H. Ahearn (1858 – April 28, 1919) was an American Major League Baseball catcher, at least for one day, during the 1880 season.

Ahearn played in one game for the Troy Trojans of the National League on June 19, 1880.

Behind the plate, he had two putouts, five assists, and two errors for a fielding percentage of .778.

At the plate, he went 1-for-4 for a .250 batting average, and he scored one run.

This biographical article relating to an American baseball catcher born in the 1850s is a stub.