• Jack Duncan
  Jack Duncan
  John L. Duncan was a rugby union player who represented Australia.Duncan, a scrum-half, was born in Sydney, New South Wales and claimed 1 international rugby cap for Australia.-References:...
  
  , John L Duncan,(1900-1969), Australian rugby union player
• John Riley Duncan
  John Riley Duncan
  John Riley "Jack" Duncan was a renowned Texas lawman with service as a Dallas police officer, Texas Ranger, and detective. He is most well known for his significant contributions to the capture of John Wesley Hardin....
  
  , John Riley "Jack" Duncan (1850-1911), Texas lawman

See also

• Jack Duncan-Hughes, Australian politician
• Walter Jack Duncan
  Walter Jack Duncan
  Walter Jack Duncan was a war artist for the United States Army during World War I.-Biography:Walter Jack Duncan was born in Indianapolis, Indiana. He lived there with his family, which included a number of prominent actors, until he finished high school...
  
   (1881–1941), American war artist
• John Duncan (disambiguation)