William Byrne
William, Bill or Billy Byrne may refer to:
- William Byrne (boxer), former boxer from New Zealand
- William Byrne (Catholic), Irish missionary and educator
- William Byrne (engraver), British artist
- William Byrne (painter), American painter
- William Byrne (priest), Irish priest
- William A. Byrne, Irish poet and educator
- William D. Byrne Jr., United States Navy admiral
- William Draper Byrne, Roman Catholic bishop of Springfield, Massachusetts, United States
- William Henry Byrne, Irish architect
- William [Matthew Byrne Sr.], American judge
- William Matthew Byrne Jr., American judge, and son of William Matthew Byrne Sr
- William Michael Byrne, Irish revolutionary
- William Patrick Byrne, member of the British Civil Service
- William Pitt Byrne, British newspaper editor and proprietor of The Morning Post
- William T. Byrne, American politician in New York
- Bill Byrne (American football), American football player
- Bill Byrne (athletic director), American collegiate athletic director
- Bill Byrne (footballer, born 1896), Australian footballer for Fitzroy
- Bill Byrne (footballer, born 1931), Australian footballer for Melbourne
- Bill Byrne (politician), Member of the Queensland Parliament
- Bill Byrne (sports entrepreneur) , founder of the first women's professional basketball league
- Billy Byrne (footballer), English footballer
- Billy Byrne (hurler), Irish retired hurler