John Callaghan may refer to: John Callaghan (physician) (1923–2004), Canadian cardiac surgeon John Callaghan (Galway), Irish murder victim John Callaghan (musician) (born 1969), British musician John Callaghan (screenwriter), see List of Republic of Doyle episodes John Callaghan (footballer), see List of Sheffield Wednesday F.C. players See also John Callahan (disambiguation) John O'Callaghan (disambiguation)