Venom, or the Venom Symbiote, is an alias used by several fictional characters appearing in American comic books published by Marvel Comics, commonly in association with Spider-Man. Venom made his first appearance in The Amazing Spider-Man #300 (May 1988).
Venom was originally conceived as a supervillain, but has since become more of an antihero. Venom is a symbiote, a sentient alien, with a gooey, almost liquid-like form. As with real world symbiotes, it requires a host, usually human, to bond with for its survival. After bonding, the symbiote endows its enhanced powers upon the host. When the Venom Symbiote bonds with a human, that new dual-life form refers to itself as "Venom".
The Venom Symbiote's first known host was Spider-Man, who eventually separated himself from the creature when he discovered its true nature. The Symbiote went on to merge with other hosts, most notably Eddie Brock, its second and most infamous host, with whom it first became Venom and one of Spider-Man's archenemies. According to S.H.I.E.L.D., it is considered one of the greatest threats to humanity, alongside Magneto, Doctor Doom, and Red Skull.
Comics journalist and historian Mike Conroy writes of the character: "What started out as a replacement costume for Spider-Man turned into one of the Marvel web-slinger's greatest nightmares." Venom was ranked as the 22nd Greatest Comic Book Villain of All Time in IGN's list of the top 100 comic villains. IGN also ranked Mac Gargan's incarnation of Venom as #17 in their list of "The Top 50 Avengers", while the Flash Thompson incarnation was ranked as #27. The character was listed as #33 on Empire Magazine's 50 Greatest Comic Book Characters.