Dennis J. O'Neil, also known as Denny O'Neil (May 3, 1939 – June 11, 2020) was an American comic book writer and editor. He worked for Marvel Comics and DC Comics from the 1960s through the 1990s. He was a Group Editor for the Batman family of titles until his retirement. O'Neil was born in St. Louis, Missouri.
O'Neil died on June 11, 2020 from cardiopulmonary arrest in Nyack, New York at the age of 81.