Brian O'Neill may refer to:
Arts and entertainment[edit]
- Brian D. O'Neill (born 1949), American author and attorney
- Brian O'Neill (journalist) (c. 1900–1975), English and Irish journalist and author
- Brian O'Neill, fictional Irish gangster in Mafia II
Sports[edit]
- Brian O'Neill (ice hockey, born 1929), Canadian executive in the National Hockey League
- Brian O'Neill (ice hockey, born 1988), American ice hockey player
- Brian O'Neill (American football) (born 1995), American football offensive tackle
Others[edit]
- Brian McPhelim O'Neill (died 1574), lord of Lower Clandeboye
- Brian MacArt O'Neill (died 1607), member of the O'Neill Dynasty
- Brian J. O'Neill (born 1949), American politician
- Brian O'Neill (superintendent) (1941–2009), American superintendent of the Golden Gate National Recreation Area
- Brian O'Neill (died 1260), High King of Ireland
- Brian C. O'Neill (born 1965), American earth system scientist and demographer
- Brian O'Neill, Baron Dungannon (died 1562), Irish aristocrat
- Sir Brian O'Neill, 2nd Baronet (died 1694), Irish landowner, barrister and judge