Duncan is a Scottish surname. The Scottish Gaelic name Donncheann or Donnchadh are bynames composed of the elements donn, meaning "brown" or "dark" from Donn a Gaelic God; and chadh, meaning "chief" or "noble".[1][2][3] In some cases when the surname was used in County Sligo, Ireland, it is an Anglicized form of the Irish Gaelic name MacDonough or Mac Donnchadha and Ó Duinnchinn, meaning "descendant of Donncheann". The surname Duncan is represented in Scottish Gaelic as MacDhonn.
- C Duncan, born Christopher Duncan, Scottish composer and musician whose debut album Architect was nominated for the 2015 Mercury Prize
- Gary Duncan (1946–2019), American guitarist and singer
- Johnny Duncan (country singer) (1938–2006), American singer
- Lesley Duncan, English singer and songwriter
- Little Arthur Duncan (1934–2008), American blues harmonica player, singer, and songwriter
- Molly Duncan (1945–2019), Scottish tenor saxophonist
- Tim Duncan (singer), Southern Gospel singer
- Trevor Duncan, English composer
- Zélia Duncan, Brazilian singer and songwriter
- Alan Duncan (born 1957), British politician
- Arne Duncan (born 1964), U.S. Secretary of Education (2009–2015)
- Charles Duncan Jr. (1926–2022), U.S. Secretary of Energy (1979–1981)
- Frank I. Duncan (1858–1946), American politician, lawyer, judge and newspaper publisher
- Jimmy Duncan, (born 1947), American politician, U.S. Representative from Tennessee's 2nd congressional district (1988–2019)
- John Duncan Sr., (1919–1988), American politician, U.S. Representative from Tennessee's 2nd congressional district (1965–1988), father of Jimmy Duncan
- Kirsty Duncan (born 1966), Canadian politician and Deputy Leader of the Government in the House of Commons
- Leslie Duncan (1880–1952), newspaper editor and politician in South Australia
- Mike Duncan (born 1951), chairman of the Board of Governors of the United States Postal Service and former chairman of the Republican National Committee in the United States
- Peter Duncan (Australian politician) (born 1945), Labor representative in South Australian and federal parliaments
- Peter Duncan (British politician) (born 1965), Scottish politician, Member of Parliament from Galloway and Upper Nithsdale (2001–2005)
- Sir Walter Gordon Duncan (1885–1963), South Australian pastoralist and MLC
- Walter Hughes Duncan (1848–1906), South Australian pastoralist and MHA for Burra
- Walter Leslie Duncan (1883–1947), Australian Senator for New South Wales
- Wesley Duncan (b. 1980), American politician and member of the Nevada Assembly
- William Addison Duncan (1836–1884), U.S. Representative from Pennsylvania's 19th congressional district (1883–1984)
- Alexander Duncan (1884–1959), British long-distance runner
- Alex Duncan (1900–1984), Australian rules football player
- Andy Duncan (basketball) (1922–2006), American basketball player
- Bobby Duncan (born 1945), Scottish footballer
- Bobby Duncan (footballer, born 2001)
- Cecil Duncan (1893–1979), Canadian ice hockey administrator
- Chris Duncan (1981–2019), American baseball player
- Dave Duncan (baseball) (born 1945), Major League Baseball player and pitching coach, father of Chris Duncan and Shelley Duncan
- Darryl Duncan, Australian rugby league footballer
- Eric Duncan (born 1984), American baseball coach
- George Duncan (golfer) (1883–1964), Scottish golfer
- Ian Duncan (born 1961), Kenyan rally driver
- Jaelyn Duncan (born 2000), American football player
- Jean Duncan (umpire), Scottish hockey umpire
- Jeff Duncan (baseball) (born 1978), American baseball player and coach
- John Duncan (footballer) (1949–2022), Scottish footballer who notably played for Dundee and Tottenham Hotspur
- Johnny Duncan (footballer) (1896–1966), Scottish international footballer and manager, who was most notably with Leicester City
- Jon Duncan (born 1975), British orienteer
- Jonathan Duncan (swimmer) (born 1982), New Zealand swimmer
- Katie Duncan (born 1988), New Zealand association footballer
- Ken Duncan (American football) (born 1946), American football player
- Mariano Duncan (born 1963), Dominican baseball player
- Rick Duncan (born 1941), American football player
- Ross Duncan (born 1944), Australian cricketer
- Sam Duncan, Westmeath Gaelic footballer
- Scott Duncan (footballer) (1888–1976), former Scottish football player and manager
- Shelley Duncan, American baseball player
- Tim Duncan (born 1976), American basketball player
- Vern Duncan (1890–1954), American baseball player
- Alasdair Duncan, Australian writer
- Dave Duncan (writer) (1933–2018), Canadian writer
- Glen Duncan (born 1965), British author
- Isabelle Wight Duncan (1812–1878), Scottish author
- Jane Duncan (1910–1976), pseudonym of Scottish writer Elizabeth Jane Cameron
- John Shute Duncan (1768–1844), English academic, writer, and museum curator
- Lois Duncan (1934–2016), American writer of children's books
- Mary Lundie Duncan (1814–1840), Scottish poet and hymn-writer
- Philip Bury Duncan (1772–1863), English academic, writer, and museum curator
- Robert Duncan (poet), American beat poet
- Sara Jeannette Duncan (1861–1922), Canadian author and journalist
- Bruce Duncan (born 1938), British priest and founder
- Carl Porter Duncan (1921–1999), professor of experimental psychology at Northwestern University, US
- Dan Duncan (1933–2010), American businessman
- David Duncan, government witness in the Enron scandal
- David Douglas Duncan (1916–2018), American photojournalist
- David F. Duncan, epidemiologist and drug policy adviser to former US President Bill Clinton
- Donald F. Duncan Sr., American entrepreneur and inventor, most commonly associated with Yo-yos
- Gary Duncan, defendant in case Duncan v. Louisiana decided by the US Supreme Court
- George Smith Duncan, a tramway and mining engineer
- Graham Duncan (botanist), botanist at Kirstenbosch Botanic Garden, South Africa
- Helen Duncan (1897–1956), Scottish medium
- Henry Duncan (minister), founder of the first Trustee Savings Bank
- Herbert Osbaldeston Duncan (1862–1945), English racing bicyclist, journalist, and pioneer of the British automobile industry
- Iain Duncan Smith, British politician
- Isadora Duncan, American dancer
- Jonathan Duncan (currency reformer) (1799–1865), British advocate of reforming the monetary system
- Jonathan Duncan (Governor of Bombay) (1756–1811)
- Joseph Edward Duncan (1963–2021), American convicted serial killer and child molester
- Kath Duncan (1888 or 1889 – 1954), Scottish communist activist
- Ken Duncan (photographer) (born 1954), Australian photographer
- Leslie Duncan (1880–1952), newspaper editor and politician in South Australia
- Marion Moncure Duncan (1913–1978), American businesswoman and lineage society leader
- Mary Ellen Duncan (died 2022), American academic administrator and teacher
- Mike Duncan (podcaster), American history podcaster and writer
- Pearl Duncan, Australian retired teacher, anthropologist, academic and Aboriginal elder.
- Scott Duncan (businessman), American billionaire
- Stephen Duncan (1787–1867), American plantation owner in the Antebellum South
- Stewart Duncan (philosopher), American philosopher
- Thomas Eric Duncan (1972–2014), the first Ebola victim of the 2014 West African outbreak to develop symptoms while in the US
- Vender Duncan (1928–1959), American serial killer
- Walter Jack Duncan (1881–1941), war artist for the US Army during World War I
- Warren W. Duncan (1857–1938), American jurist
- William Duncan (American physician) (1860–1900), American physician and politician
- William Duncan (philosopher) (1717–1760), Scottish natural philosopher and classicist
- Karen Beecher-Duncan, supporting character (and sometime member) of the Teen Titans (DC Comics)
- Lily Duncan, a fictional character from Mona the Vampire
- Mal Duncan, supporting character (and sometime member) of the Teen Titans (DC Comics)
- Tammy & Tommy Duncan, supporting characters from The Mighty Ducks.
- Tyler Duncan and Mrs. Duncan are secondary characters in Big Time Rush
- Veronica Duncan, supporting character in Young Sheldon
- Ian Duncan, a character in the TV series Community, played by actor John Oliver
- King Duncan, of Shakespeare's Macbeth
- Duncan, (Walter Sparrow) Robin of Locksley's companion in the 1991 film Robinhood Prince of Thieves.
- Duncan Idaho, a Mentat from Frank Herbert's Dune
- Tara Duncan, the titular character of the French fourteenth-book series by Sophie Audouin-Mamikonian. Unfortunately, only the first two have been translated into English.
- Carter Duncan, the main antagonist of The Perfect Guy (2015 film)
Ó hÓgáin, Dáithí (1999). The Sacred Isle: Belief and religion in pre-Christian Ireland. Boydell & Brewer. pp. 27, 58.
Ó hÓgáin, Dáithí (1991). Myth, Legend & Romance: An encyclopaedia of the Irish folk tradition. Prentice Hall Press. pp. 165–166, 154.