Firebreather is a comic book created by Phil Hester and Andy Kuhn and published by Image Comics. Set in the Image Universe, the series focuses on the life of a teenage half-dragon Duncan Rosenblatt. The story has been told in a mini-series (2003) and a one-shot (2004). An ongoing series started in May 2008, and a film based on the series aired on Cartoon Network on November 24, 2010. Following the publication of a crossover series, The Pact, Duncan was incorporated into Invincible as a supporting character.

The character was originally part of a Young Avengers proposal that Hester put together for Marvel Comics, initially conceived to be the son of Fin Fang Foom, a concept later referenced in the Marvel Comics series The Unbelievable Gwenpool.

It was reworked into a miniseries at Image Comics in 2003. A one-shot followup, The Iron Saint was published in 2004. The character returned in an ongoing series in 2008. Four issues of the ongoing series were published, followed by a third volume in 2010. Two issues of this Holmgang story were released, leaving the series unfinished.

Duncan Rosenblatt is the son of the human Margaret Rosenblatt and the 100 ft. dragon Belloc who rules over the monsters. This makes Duncan a hybrid of both species. He gains powers because of this with a side effect of physical reptilian traits and recurring temperamental issues.

Duncan and Margaret move to Progress, Utah where Duncan begins his first day at yet another new school, trying to fit in despite his unusual physical appearance. Duncan and Margaret are supported by Col. Frank Barnes, the leader of a military unit called Strikeforce that formerly hunted Belloc and other monsters until a truce was made. However, there are great many obstacles to this goal, particularly his new principal who doesn't like him and a bully named Troy. He does make a few friends amongst other outcasts like Kenny and Dre, as well as Jenna Shwartzendruber, a senior peer counselor whom he develops feelings for. At his father Belloc's place, Duncan goes through rough training for the weekend. Belloc is training him not only to be powerful, but he wants Duncan to learn things the hard way. Back at school, Duncan throws a dodgeball hard into Troy's face during gym class. So for a little payback, Troy tries to set Duncan up by hiding his dad’s gun in his locker. It works, but the reaction is far more than what Troy wanted. This leads to Duncan seriously thinking about his control over his emotions and if he truly belongs in the world with humans.

When he returns home, it is demolished and Margaret is missing. He tracks down his mother and her kidnapper, a monster from Monster Island. He and the monster have a brutal fight which ends (at least as far as Duncan is concerned) with Duncan blasting the monster with flame, leaving the monster badly burned but alive. This changes when Belloc arrives on the scene and impales the monster with his tail. Duncan figures out that Belloc arranged the kidnapping to test him and threatens to kill him if he ever endangers his mother again. After Duncan flies away, Belloc smiles to himself, saying, "There's my boy".

Duncan's class is taken abroad by "Mr. Martinez" the Spanish teacher, who shows them the sights of London, before making their way to Spain. While in London, the group hears the story of "The Iron Saint", a long forgotten being that was created to fight, and survive, the King of the Monsters. The suit of armor has been passed down for generations and generations, and now it's just a museum piece. Duncan learns of its history, and its connection to him, and can't help but be curious. When he and Kenny investigate, they find that the suit has been brought back to life and it's out to get Duncan. The wearer of the armor turns out to be Mr. Martinez, who is revealed to be not only an S.O.S. escort but a survivor of an attack on a Cuban village and a former agent of Strikeforce. He attempts to use the armor to kill Duncan as revenge for Belloc killing his parents when he was a kid. However, Duncan is saved due to his half-human heritage, since the armor cannot draw human blood or else it will be destroyed, and kill humanity, and all life on Earth. The Iron Saint dissolves and Martinez is apprehended by Barnes. On a plane back home, Duncan accidentally scratches Jenna’s cheek but she claims she didn’t feel it.

Belloc becomes furious when Duncan refuses to visit him on Father’s Day and goes on a rampage burning a neighborhood. Duncan, now taking the name ‘Firebreather’ is told of this by passing bullies, and flies off to stop him. Shadowhawk, Invincible, and Zephyr Noble, all get word of Belloc’s rampage as well and join in together to fight him. Things spur out of control until Duncan yells at the three other teen heroes to cease their attack and reasons with his father to halt his assault. The four later decide to form a friend group and are put through a series of adventures.