William Duffy

• Bill Duffy (basketball), American basketball player and player agent
• Bill Duffy (sportsman), Australian sportsman
• Billy Duffy, English musician
• Billy Duffy (hurler), Irish hurler
• William Duffy, a pseudonym of William Dufris, an American voice actor
• William Duffy (bishop), English Roman Catholic bishop
• William Duffy (politician), Irish nationalist politician
• William James Duffy, Canadian politician
• William J. Duffy, American jurist and legislator