John Duffy may refer to:
Sportspeople John Duffy (footballer, born 1886) (1886–?), English football centre half for Bradford City John Duffy (footballer, born 1922) (1922–1996), Scottish football right back for Clyde and Norwich John Duffy (footballer, born 1929) (1929–2004), Scottish football wing half for Celtic, Arbroath and Southend John Duffy (footballer, born 1943), Scottish football wing half for Raith, Dunfermline, Darlington and Australian clubs John Duffy (Gaelic footballer), Gaelic football player John Duffy (rugby league) (born 1980), rugby league player John Duffy (soccer) (1905–1984), American soccer player
Others John Duffy (composer) (1926–2015), American composer John Duffy (economist) (born 1964), American economist John Duffy (mobster) (died 1924), American gang member, member of the North Side Gang John Duffy (writer), Canadian writer and political strategist John Duffy and David Mulcahy (both born 1959), the Railway Rapists, British rapists and murderers John A. Duffy (1884–1944), American bishop John F. Duffy (born 1963), legal academic John Gavan Duffy (1844–1917), Australian politician John J. Duffy, American Medal of Honor recipient John J. Duffy Jr. (1933–2019), American criminal defense attorney John Duffy (medical historian) (1915–1996), University professor & author of several books on U.S. medical history
See also Jack Duffy (actor) (1882–1939), American film actor Jack Duffy (1926–2008), Canadian entertainer