Denny O'Neil is best known for his work as a comic book writer and editor at Marvel and DC starting in the 1970s. Denny is best known for his work on Batman, Green Lantern/Green Arrow, Detective Comics, Iron Man, The Shadow and The Question. In addition to his work in comics, Denny is an accomplished novelist.

Denny's credits as a writer include: 1st Issue Special, Abbott and Costello, Adventure Comics, All Star Western, Amazing Spider-Man, Amazing X-Men, Armageddon 2001, The Atom, Atom & Hawkman, Azrael, Azrael: Agent of the Bat, Batlash, Batman, Batman and Superman, Batman: Birth of the Demon, Batman: Black and White, Batman: Gordon of Gotham, Batman Chronicles, Batman Family, Batman: Legends of the Dark Knight, Batman: Sword of Azrael, Beware the Creeper, Billy the Kid, Black Lightning, Bomba the Jungle Boy, Brave and the Bold, Captain America, Challengers of the Unknown, Chamber of Darkness, Daredevil, DC Comics Presents, DC/Marvel, DC Special Series, Detective Comics, Diana Prince: Wonder Woman, Doc Savage, Epic Illustrated, The Flash, Flash Gordon, Further Adventures of Indiana Jones, Ghost Manor, Ghost Rider, Green Arrow, Green Lantern, Green Lantern/Green Arrow, Hercules, House of Mystery, Hulk, Iron Man, Iron Wulf, Isis, JLA, The Joker, Justice League of America, Justice League Task Force, Kamandi, Kid Colt Outlaw, Legends of the DC Universe, Marvel Preview, Marvel Super Special, Marvel Tales, Modeling With Millie, Moon Knight, Ms. Tree Quarterly, Nightwing, Patsy and Hedy, The Phantom Stranger, Power Man and Iron Fist, The Question, Rawhide Kid, Richard Dragon: Kung Fu Fighter, Savage Tales, Secret Origins, Sensational Spider-Man, The Shadow, Shazam!, Sherlock Holmes, Showcase, Space Adventures, The Spectre, The Spirit, Star Trek, Strange Adventures, Strange Sports Stories, Strange Suspense Stories, Strange Tales, Super-Team Family, Superman, Sword of Sorcery, Tarzan, Team America, Time Warp, Tower of Shadows, Two-Gun Kid, Uncanny X-Men, The Unexpected, Unknown Worlds of Science Fiction, Vampirella, Weird Western Tales, Weird Worlds, What If?, The Witching Hour, Wonder Woman, World's Finest Comics and more!

Denny’s novels include: The Bite of Monsters (Belmont, 1971), Dragon’s Fists – Richard Dragon, Kung Fu Master (1974), Secret Origins of the Super DC Heroes (Crown Publishing Group, April 1976), The Super Comics (Scholastic Book Services 1981), Batman Knightfall (1994), Green Lantern Hero’s Quest (2005), Batman Begins (2005), DC Universe: Helltown (2006) and The Dark Knight (2008). Denny's novella's include: