Duffy is a surname of Irish origin that comes from the original Irish name Ó Dubhthaigh, meaning descendant of Dubthach. Dubthach was an Old Irish first name meaning "black".

Variations include: Duffey, Duffee, Duff, Duthie, O'Duffey, O'Duffy, Duffe, O'Duffe, Dufficy, Doey, Dohey, Doohey, Duhig, Duhigg, Dowey and O'Dowey. The name originates from Connacht.

It may refer to:

• Charles Gavan Duffy, Irish nationalist poet, later Australian colonial politician
• Chris Duffy, several people
• David Duffy (banker) (born 1960/61), Irish banker
• Eamon Duffy, historian
• Francis Noel Duffy, Irish Green Party politician, TD for Dublin South-West since 2020
• Gabriel Duffy, Irish writer
• George Gavan Duffy, Irish politician
• James Duffy (Irish publisher), an Irish publisher of Nationalist and Roman Catholic books, bibles and religious texts
• James Duffy (VC), Irish recipient of the Victoria Cross in 1917
• Jim Duffy (journalist), author, political commentator, and Irish advisor to Australia's Republic Advisory Committee
• Joe Duffy, Irish radio personality
• Joseph Duffy (bishop), Irish Catholic bishop
• Keith Duffy, Irish musician from Boyzone
• Luke Duffy, trade unionist and politician
• Mark Duffy (banker), Irish banker
• Martin Duffy (filmmaker), Irish filmmaker and writer
• Mik Duffy, Irish filmmaker and journalist on film
• Shane Duffy, Irish footballer
• Thomas Duffy (VC) (1805–1858), Irish recipient of the Victoria Cross in 1857

• Bill Duffy (1866–1959), sportsman
• Charles Gavan Duffy (1816–1903), Irish nationalist poet, later Australian colonial politician
• Frank Gavan Duffy (1852–1936), judge
• Kevin Duffy (footballer) (1897–1977) Australian footballer
• Max Duffy (born 1993), player of Australian and American football

• Ron Duffy, New Zealand rugby league footballer

• Amanda Duffy (died 1992), Scottish murder victim
• Carol Ann Duffy, Poet Laureate of the United Kingdom
• Darryl Duffy, Scottish football player
• Jim Duffy (footballer), former football (soccer) player and manager
• Neil Duffy Sr., Scottish footballer
• Neil Duffy Jr., Scottish-South African footballer (son of above)

• Aimée Duffy, real name of Welsh singer Duffy
• Richard Duffy, Welsh footballer

• Adam Duffy, English professional snooker player
• Billy Duffy, British musician
• Brian Duffy (photographer), British photographer
• Brian Duffy, real name of British drummer Jet Black of The Stranglers
• Christopher Duffy, British historian
• Hetha Duffy, co-founder of Bluemoose Books
• John Duffy and David Mulcahy, British murderers
• Kevin Duffy (publisher), co-founder of Bluemoose Books
• Martin Duffy, keyboardist with Primal Scream
• Maureen Duffy, British writer
• Nick Duffy, British songwriter
• Patrick Duffy (British politician)
• Paul Duffy, bass guitarist for The Coral
• Peter Duffy, British Barrister
• Philip Duffy, English composer of sacred music
• Stephen Duffy, British songwriter

• Barbara Duffy (born 1959), American dancer
• Brian Duffy (astronaut), American astronaut
• Bruce Duffy, Irish-American novelist, author of The World as I Found It
• Charles John Duffy, American WWII pilot, namesake of USS Duffy
• Chris Duffy (baseball), American baseball player
• Danny Duffy, American baseball player
• Helen Duffy, American actress, known for Breakdown
• Francis P. Duffy, Canadian-American Catholic priest
• Gerald Duffy, American screenwriter
• Hugh Duffy, American baseball player
• J. C. Duffy, American cartoon artist
• James E. Duffy Jr., United States Democratic Party nominee for the Hawaii Supreme Court
• Jimmy Duffy, Irish-Canadian distance runner
• Jim Duffy (baseball coach) (born 1974), American college baseball coach
• Jo Duffy, American comics book writer
• John Duffy (soccer), U.S. soccer player at 1928 Summer Olympics
• John A. Duffy, American Roman Catholic bishop
• Julia Duffy, American actress
• Karen Duffy, American model and actress
• Kevin Duffy (1933–2010), American judge
• Matt Duffy, American baseball player
• Megan Duffy (born 1984), American basketball player and coach
• Megan Duffy (actress) (born 1979), American actress and producer
• Meghan Duffy, American biologist
• Mike Duffy, Canadian senator, retired television journalist
• Pat Duffy, American skateboarder
• Patricia Lynne Duffy, synesthete
• Patrick Duffy (born 1949), American television actor
• Robert Duffy (politician), American mayor
• Roger Duffy (architect), American architect
• Romney Duffey, American/Canadian scientist
• F. Ryan Duffy, American politician
• Sean Duffy, a politician from Wisconsin
• Thomas C. Duffy, composer, conductor, Yale University professor
• Thomas J. Duffy, American craftsman/designer
• Troy Duffy, American actor and film director
• Uriah Duffy, bass player in Whitesnake and many other bands

• James Duffy (disambiguation)
• Martin Duffy (disambiguation)
• Michael Duffy (disambiguation)
• William Duffy (disambiguation)

• A. D. Duffey, California legislator
• Arthur Duffey, American athlete
• Doug Duffey, American blues musician
• Eliza Bisbee Duffey, American feminist
• George Frederick Duffey, President of the Royal College of Physicians of Ireland
• Ike Duffey, American businessman and sports executive
• Jett Duffey, American football quarterback
• Jim Duffey, Virginia Secretary of Technology, 2010–2014
• Joe Duffey, rugby union
• John Duffey (soldier), American soldier who fought in the American Civil War
• John Duffey, American bluegrass musician
• Joseph Duffey, American academic administrator
• Mike Duffey, Ohio politician
• Romney Duffey, American nuclear scientist
• Thomas J. Duffey, member of the Wisconsin State Assembly
• Todd Duffey, American actor
• Tyler Duffey, American baseball player
• Warren J. Duffey, U.S. Representative from Ohio
• William S. Duffey Jr., United States District Judge

• Officer Duffy, corrupt police officer in RoboCop 2; played by Stephen Lee (actor)
• Kieran Duffy, fictional character from Red Dead Redemption 2

• Duff (surname)
• Dufy, a French surname