John Stephen Michael "Deacon" Donahue (June 23, 1920 – March 6, 2008) was a relief pitcher in Major League Baseball who played from 1943 through 1944 for the Philadelphia Phillies. Listed at 6 ft 0 in (1.83 m), 180 lb (82 kg), Donahue batted and threw right-handed. He was born in Chicago, Illinois.
Donahue was one of several players who only appeared in the majors during World War II. In eight relief appearances, he posted a 0–2 record with a 6.75 earned run average with no saves, giving up 11 runs (one unearned) on 22 hits and three walks while striking out three in 131⁄3 innings of work.
Following his baseball career, Donahue worked as a movie theatre projectionist in the Chicago area for 40 years. He died in Glenview, Illinois, at the age of 87.