Dennis O'Neil (often credited as Denny O'Neil) (b May 3, 1939) is an American comics writer and editor. Amongst many other roles in a long career he served as editor of G.I. Joe: A Real American Hero, starting with issue #7 and continuing through until issue #48.
O'Neil's numerous other comics credits include a heavily acclaimed run with Neal Adams on Green Lantern/Green Arrow in 1969 which saw comics start to address major social and political issues and for which he received three Shazam Awards; and a radical redefining of Batman in the early 1970s that took the character back to his grim loner roots. He has also worked on many other comics for Marvel Comics, DC Comics and Charlton Comics.