Hellboy is a fictional Dark Horse Comics character created by Mike Mignola. He first appeared in San Diego Comic-Con Comics #2.
As a demon named Anung Un Rama, Hellboy was brought to Earth as an infant by Nazi occultists. He was rescued by Allied forces and raised by the United States’ Bureau for Paranormal Research and Defense (BPRD). He grew up to be a large red-skinned demon with a tail, horns (which he files down to stumps), and a big stone right hand. Although a bit gruff, he shows none of the malevolence thought to be intrinsic to demons and works with other strange creatures in the B.P.R.D. He has been dubbed as the "World's Greatest Paranormal Investigator."
Hellboy has been featured in a sequence of comic book mini-series published by Dark Horse Comics, influenced by vintage adventure and horror fiction. They have been some of the most successful comics not published by Marvel, DC, or Image Comics.
The comics were adapted into a 2004 film starring Ron Perlman as Hellboy with a sequel and two straight to DVD animated films on the way.

Hellboy is a creature summoned in the final months of World War II by a fictional version of Grigori Rasputin, on a small island just off the coast of Scotland ('Tarmagant Island'), having been commissioned by the Nazis to change the tide of war ("Project Ragna Rok"). Hellboy appeared in a fireball in a ruined church in East Bromwich, England, December 23, 1944. He proved not to be a devil, but a little boy-like creature (with red skin, horns, a tail, and a large stone right hand) —hence the name given by Professor Trevor Bruttenholm (pronounced Broom).

Taken by the U.S. forces to an Air Force base somewhere in New Mexico, Hellboy was raised by the United States Army and by the Bureau for Paranormal Research and Defense, a U.S. agency dedicated to combating occult threats. He was granted honorary human status by the United Nations in 1952.

As an adult, Hellboy became the primary agent for the B.P.R.D. alongside several other human and quasi-human agents. His fellow agents included Abe Sapien, an amphibian humanoid ("ichthyo sapien"); Liz Sherman, a pyrokinetic; and Roger, an unusually large homunculus.

In the comics Hellboy is at least semi-famous, having been granted "honorary human" status by the UN in the 1950s and being known as the "world's greatest paranormal investigator." As such he interacts regularly with normal humans, most of whom are not presented as overtly reacting to his strange appearance (though his primary interactions in the comics are with law enforcement officials from different organizations, the military, and various "scholars of the weird"). In the film version, however, he is kept under lock and key and considered simply an "urban legend" by the general populace.

Hellboy's adventures in the comics span the 1940s to the present day and involve elements such as sorcerers, Nazis, the Thule Society, hollow earth explorers, werewolves, vampires, ghosts, and other oddities such as the Ogdru Jahad.

Several of the storylines deal with Hellboy's Right Hand of Doom and its purpose in initiating the Apocalypse. Much in the same vein as fellow comic-book superheroes Daredevil, Batman, Blade, and Wolverine, Hellboy is a hero constantly haunted by the knowledge of his past.

Hellboy's superhuman abilities stem from his demonic nature. While his specific powers and abilities have never been explicitly described in the comics, Hellboy is much stronger and more physically durable than an ordinary human being. He has been savagely beaten by large monsters on several occasions and survived, often with relatively minor injuries. On one occasion, he directly charged an MG-42 machine gun and took numerous bullets to the chest before destroying the gun.

The extent of Hellboy's strength is unclear, but he has, for example, torn down a large tree and hurled it at an opponent. He has also thrown opponents weighing at least four to five hundred pounds.

Hellboy's right hand, referred to as the Right Hand of Doom, consists of a large forearm and hand that seems to be made from red stone. The Hand is effectively invulnerable and feels no pain, and is much like a sledgehammer when used to punch an enemy. Of course, being far larger than an ordinary human hand, the Right Hand of Doom is not very suitable for use with most objects, so he relies on his average-sized left hand to operate weapons and devices, although it has proved flexible enough to catch a fly. Because of this, he is most likely ambidextrous.

More importantly, the Right Hand of Doom also is the key to "open the pit [of hell]" and has the "power to loose and command the dragon Ogdru Jahad;" in other words, it is a catalyst that will bring about Ragnarök/Armageddon/Apocalypse etc. The comic books themselves never actually mention how the Right Hand of Doom would actually perform these tasks, it is only ever announced that this is the case and that someone or something intends to do it with or without Hellboy's consent. It is made clear that it is not even necessary for the arm to be attached to Hellboy at all, even on its own it would perform its tasks, so to prevent it falling into the wrong hands Hellboy intends to keep the arm and protect it.

In addition to his natural gifts, Hellboy carries a variety of religious items--such as holy relics, horseshoes, and herbs--in his utility belt, as well as a variety of grenades and other demolition tools. These often come in handy when fighting supernatural beasts.

Hellboy commonly carries a large pistol. In the film adaptation, the gun is called the "Samaritan," and Hellboy states that he uses special bullets containing silver shavings, holy water, and other materials to ensure the weapon's effectiveness against supernatural creatures.