John or Johnny Duncan may refer to:
Arts and entertainment John Duncan (painter) (1866–1945), Scottish painter John Duncan (harpist) (1904–1998), English musician Johnny Duncan (actor) (1923–2016), American actor Johnny Duncan (bluegrass musician) (1931–2000), American skiffle and bluegrass musician Johnny Duncan (country singer) (1938–2006), American country-music singer John Duncan (American artist) (born 1953), American artist and musician Big John Duncan (born 1958), Scottish punk musician
Law, government, and politics John Holt Duncan (1820–1896), American lawyer and judge, co-founder of Beta Theta Pi at Miami University Sir John Duncan (Australian politician) (1845–1913), South Australian pastoralist and politician John Duncan (New Zealand politician, born 1848) (1848–1924), New Zealand member of parliament John D. C. Duncan Jr. (1884–1958), American politician and lawyer John Edward Duncan (1884–1959), member of the New Zealand Legislative Council John Duncan Sr. (1919–1988), U.S. representative from Tennessee Jock Duncan (diplomat) (John Spencer Ritchie Duncan, 1921–2006), British administrator in Sudan and diplomat John Alton Duncan (1932–2007), Manitoba judge John Duncan (American government official) (born 1945), official in the U.S. Department of the Treasury Jimmy Duncan (politician) (John James Duncan Jr., born 1947), U.S. Representative from Tennessee, son of John Duncan Sr. John Duncan (Canadian politician) (born 1948), member of parliament from British Columbia John Duncan (diplomat, born 1958), British diplomat
Military John Duncan (British Army officer, born 1870) (1870–1960), British general Sir John Duncan (British Army officer, born 1872) (1872–1948), British general
Religion John Dongan (or John Duncan, died 1413), Manx priest in the Isle of Man and Ireland John Duncan (English writer) (1721–1808), English priest, miscellaneous writer and army chaplain John Duncan (theologian) (1796–1870), Free Church of Scotland minister, missionary, hebraist and orientalist John Duncan (English archdeacon) (born 1933), English Anglican priest, archdeacon of Birmingham, 1985–2001
Science, technology and medicine John Duncan (weaving writer) (fl. 1800–1818), Scottish writer on weaving John Duncan (botanist) (1794–1881), Scottish weaver and botanist John Duncan (surgeon) (1839–1899), Scottish surgeon, president of the Royal College of Surgeons of Edinburgh John Charles Duncan (1882–1967), American astronomer John Duncan (neuroscientist) (born 1953), British neuroscientist John S. Duncan (born 1955), British neurologist
Sports John William Duncan (1885–1963), Welsh field hockey player Johnny Duncan (footballer) (1896–1966), Scottish football player and manager associated with Leicester City Art Duncan (John Arthur Duncan, 1891–1975), Canadian ice hockey player Ross Duncan (John Ross Duncan, born 1944), Australian cricketer John Duncan (footballer) (1949–2022), Scottish football player and manager
Others John Shute Duncan (1768–1844), English academic, writer, and museum curator John Duncan (explorer) (1805–1849), British soldier and explorer in Africa John Riley Duncan (1850–1911), Texas lawman John H. Duncan (1855–1929), American architect John Duncan (historian) (1938–2022), American historian and writer
See also Jon Duncan (born 1975), British orienteering world champion Jack Duncan (disambiguation) Jonathan Duncan (disambiguation)