Ultimate Six is a seven-issue comic book limited series and crossover between Spider-Man and the Ultimates (2003), featuring the Ultimate Marvel version of the Sinister Six. The series was written by Brian Michael Bendis, penciled by Trevor Hairsine and inked by Danny Miki.

Ultimate Six is a seven-issue limited series published by Marvel Comics from November 2003 to June 2004. The series is a crossover featuring Spider-Man and The Ultimates against the Ultimate universe incarnation of the Sinister Six. Each issue of the series was released monthly and formed a connected story arc following the events of Ultimate Spider-Man #46. The first issue debuted in November 2003, with the final issue published in June 2004.

The series has been collected in various trade paperbacks, including Ultimate Spider-Man Volume 9: Ultimate Six (2004), which collects all seven issues plus Ultimate Spider-Man #46. A hardcover collecting this and 'Ultimate Spider-Man Volume 10: Hollywood' was also released in November 2004

The story takes place after the events shown in Ultimate Spider-Man #46.

Electro wakes up from his three-week coma and goes on a rampage before being confronted by Captain America, Iron Man, and Black Widow. After appearing on TV, Kraven the Hunter and his lawyer are confronted by Captain America, Thor, Iron Man, Wasp, and Hawkeye to question him about his "enhancements". Hawkeye prevents Kraven from running off while Wasp disables the camera run by Kraven the Hunter's camera operator. The Ultimates detain the two villains in a maximum-security S.H.I.E.L.D. superhuman prison beneath the Triskelion along with Sandman, Doctor Octopus, and Green Goblin. As Hank Pym tries to get information from them during his interrogation on them, Nick Fury informs the five captives that they are detained because they have illegally altered their genetic code. Sharon Carter is having Kraven taken to his cell where he briefly assumes his gruesome and animalistic appearance that included fangs, claws, large muscles, big hands, and big feet before his inhibitor collar activates. Osborn is convinced that "There will be six" prisoners.

Pym continues his interrogation on the criminal. Osborn starts to turn into Green Goblin as Pym grows big to subdue him. Six weeks later, Pym gives a status report on his interrogation to Nick Fury and the rest of the Ultimates. Otto Octavius wants to cooperate with his captors and is granted access to a laboratory, where his metal tentacles are held. He wills his tentacles to attack and then shuts down the prison's power, releasing the others.

Iron Man investigates the ruins where he finds Pym injured and unconscious under some rubble which does not bode well for Wasp who goes to meet up with Iron Man. Nick Fury immediately sends agents to collect Peter Parker just in case Osborn goes after him. Fury introduces him to the Ultimates, who do not believe that Spider-Man is a teenager and reminds them that he has defeated all five escapees on his own. From a secret retreat, Norman Osborn places a call to Chief of Staff Stone in regard to Nick Fury.

Norman Osborn and his fellow villains take refuge in Kingpin's house in The Hamptons. The President chews out Nick Fury in regard to the call from Osborn who blackmails the government or he would publicize his treatment at the hands of S.H.I.E.L.D. Fury dispatches the Ultimates. After Doctor Octopus hacks into the Triskelion, the five escapees then attack the Triskelion. Nick Fury asks for the status of Bruce Banner and Magneto. A S.H.I.E.L.D. agent states that Magneto is still locked up.