John Monaghan may refer to:
John Monaghan, Author, johnmonaghan.com, NYPD Captain
John R. Monaghan, United States Navy officer
John James Joseph Monaghan, American prelate of the Roman Catholic Church
Rinty Monaghan (John Joseph Monaghan), flyweight boxer from Belfast
Jack Monaghan (1921–2022), New Zealand amateur wrestler
John Monaghan (businessman), New Zealand dairy executive with Fonterra