John Constantine (/ˈkɒnstəntaɪn/)^[1] (also known as Hellblazer) is a fictional character, an antihero, appearing in comic books published by DC Comics and DC Comics's imprints Vertigo. The character first appeared in The Saga of the Swamp Thing No. 37 (June 1985), and was created by Alan Moore, Steve Bissette, and John Totleben. He serves as the lead character of the comic books Hellblazer (1988–13), Constantine(2013–15), Constantine: The Hellblazer (2015–16), and The Hellblazer (2016–).

The titular Hellblazer,^[2]^[3] Constantine is a working class occult detective and con man stationed in London. He is known for his endless cynicism, deadpan snarking, ruthless cunning and constant chain smoking, but is also a passionate humanist driven by a heartfelt desire to do some good in his life. Originally a supporting character who played a pivotal role in the "American Gothic" Swamp Thing storyline, Constantine received his own comic in 1988. Pop artist Sting served as visual inspiration for the character.^[4] A live-action film was released in 2005 entitled Constantine, in which an Americanized version of the character is played by actor Keanu Reeves. Welsh actor Matt Ryan was cast in the role of Constantine for the 2014 NBC television series Constantine, a role he reprised on The CW series Arrow, as well as the animated film Justice League Dark.

The Hellblazer series was the longest-running and most successful title of DC's Vertigo imprint.^[5] Empire Magazine ranked Constantine third in their 50 Greatest Comic Characters of All Time,^[6] while IGN ranked him No. 29 in their Top 100 Comic Book Heroes, and the character ranked No. 10 in Wizard Magazine's Top 200 Comic Book Characters of All Time.