John Gallagher may refer to:

• John Gallagher (Dying Fetus), vocalist/guitarist for the American death metal band Dying Fetus
• John Gallagher Jr., actor/musician
• John Gallagher III, astronomer
• John Gallagher (baseball) (1892-1952), MLB player
• John Gallagher (basketball coach), head men's basketball coach at the University of Hartford
• John Gallagher (cartoonist)
• John Gallagher (geologist) (born 1916)
• John Gallagher (golfer)
• John Gallagher (ice hockey)
• John Gallagher (barrister), member of the board of the Australian Broadcasting Corporation
• John Gallagher (rugby league) (born 1964)
• John Anthony Gallagher, British-born All Black
• John Andrew Gallagher, British Historian
• Jack Gallagher, comedian, actor and writer
• John B. Gallagher (cartoonist)

[ Source: Wikipedia ]