• Duncan Macmillan (athlete) (born 1890), British track and field athlete competitor in the 1912 Summer Olympics
• Duncan Macmillan (Canadian politician)
  Duncan Macmillan (Canadian politician)
  Duncan Macmillan was a lawyer, judge and political figure in Ontario, Canada. He represented Middlesex East in the Canadian House of Commons from 1875 to 1887 as a Liberal-Conservative member....
  
   (1837–1903), Canadian lawyer and Member of Parliament
• Duncan Bruce MacMillan former Alberta politician.

See also

• Duncan MacMillan High School
  Duncan MacMillan High School
  Duncan MacMillan High School is a secondary school in Sheet Harbour, Nova Scotia, Canada.Duncan MacMillan is the smallest high school in the Halifax Regional School Board, but it has the largest geographical area for bussing. Duncan MacMillan hosts Grades 7–12 and has about 251–263 students...
  
  , a secondary school in Sheet Harbour, Nova Scotia, Canada