Dennis O'Neill

Dennis O'Neill may refer to:

• Dennis O'Neill (baseball) (1866–1912), 19th-century baseball player
• Dennis O'Neill (manslaughter victim), British manslaughter victim
• Dennis O'Neill (rugby league), rugby league footballer of the 1970s for Great Britain, and Widnes
• Dennis O'Neill (tenor) (born 1948), Welsh tenor

• Dennis O'Neil (1939–2020) aka Denny O'Neill, American comic book writer and editor
• Dennis Patrick O'Neil (1940–2003), Roman Catholic bishop