The Marvel Comics anthology series What If? tells alternate reality stories outside the mainstream Marvel Universe continuity, which the company sets on what it calls Earth-616. A number of these stories have been set on alternate Earths in the Marvel Comics Multiverse (i.e., multiple universes) for which Marvel has given official numerical designations.
Volume 1 (1977–1984) What if Spider-Man had joined the Fantastic Four? (based on The Amazing Spider-Man #1) Reprinted in The Best of What If? Followed by What If? #21. Alternate sequels appeared in What If? vol. 2, #35, and Paradise X. This world was designated Earth-772 in Marvel Encyclopedia: Fantastic Four. Spider-Man did eventually join the team as a member of the "New Fantastic Four" and the Future Foundation. What if the Hulk had the brain of Bruce Banner? (based on The Incredible Hulk #1) This world was designated Earth-774 in Marvel Encyclopedia: Fantastic Four. What if the Avengers had never been? (based on The Avengers #3) What if the Invaders stayed together after World War II? (considered part of Earth-616, the mainstream Marvel continuity) What if Captain America had not vanished during World War II? (based on Avengers #4) What if the Fantastic Four had different super-powers? (based on The Fantastic Four #1) This version of the team reappeared in What If? (vol. 2) #39. This world was designated Earth-7712 in Marvel Encyclopedia: Fantastic Four. What if someone else besides Spider-Man had been bitten by the radioactive spider? (based on Amazing Fantasy #15) Three different stories look at what would have happened if either Peter's class bully Flash Thompson, his would-have-been temporary girlfriend Betty Brant, or publisher J. Jonah Jameson's astronaut son John, had been bitten by the radioactive spider instead. With the exception of Betty Brant (who quits her moniker like Peter did in "Spider-Man No More!"), the protagonist dies in each story. A darker version of the Flash story is redone as What If? (vol. 2) #76. What if the world knew Daredevil was blind? (based on Daredevil #2) This issue also contained the first humor-based What If? in the series asking, "What if the spider had been bitten by a radioactive human?". What if the Avengers fought evil in the 1950s? Designated Earth-9904 in All-New Official Handbook of the Marvel Universe: A-Z Update #2 (2007). A version of this timeline was revisited in Avengers Forever, and yet another version made a cameo in Paradise X. The Agents of Atlas, a superhero team from the 1950s, was based on this concept. What if Jane Foster had found the hammer of Thor? (based on Journey into Mystery #83) The main universe's Jane Foster would eventually become the new Thor in Thor (vol. 4) #1. What if the original Marvel Bullpen had become the Fantastic Four? (based on The Fantastic Four #1) This world made a brief tongue-in-cheek appearance in Paradise X. It was designated Earth-1228 in The Official Handbook of the Marvel Universe: Alternate Universes 2005. What if Rick Jones had become the Hulk? (based on The Incredible Hulk #1) What if Conan the Barbarian walked the Earth today? (based on The Savage Sword of Conan #7 "The Citadel at the Center of Time") An alternate ending to this story can be seen in What If? #43. What if Nick Fury had fought World War II in outer space? This universe made a brief appearance in Paradise X. What if Nova had been four other people? (based on Nova #1) Instead of the random decision for Richard Rider to become Nova, the powers of Nova are transferred to a vengeful wife whose husband had been murdered, a kind and homeless black man in a universe with no superheroes, Peter Parker in a world where the radioactive spider that bit him had crippled him, and an unknown character with a villainous personality. What if Shang-Chi, Master of Kung Fu, fought on the side of Fu Manchu? (based on Master of Kung Fu #15) What if the Ghost Rider, Spider-Woman and Captain Marvel were villains? (based on Marvel Spotlight #5 and #32 and Marvel Super Heroes #12) As with issue #7, this contained three short stories with the theme of Marvel characters who strayed close to becoming villains rather than heroes in the Earth-616 universe. What if Doctor Strange were a disciple of Dormammu? (based on Strange Tales #110) What if Spider-Man had never become a crimefighter? (based on Amazing Fantasy #15) What if the Avengers fought the Kree-Skrull War without Rick Jones? (based on Avengers #96) What if the Invisible Girl of the Fantastic Four had married the Sub-Mariner? A sequel to What If? #1. What if Doctor Doom had become a hero? (based on Fantastic Four #5) This world was designated Earth-808 in Marvel Encyclopedia: Fantastic Four. What if the Hulk had become a barbarian? (based on The Incredible Hulk #205) This issue also contains the back-up humor story, "What if Aunt May had been bitten by the radioactive spider?" What if Gwen Stacy had lived? (based on The Amazing Spider-Man #121) Reprinted in The Best of What If? What if Thor and the Avengers fought the gods? (based on Thor #136) Also features the backup story "The First Uni-Mind", explaining the origins and concept of the Uni-Mind and the origin story of A'lars and Zuras. What if Captain America had been elected president? (based on Captain America #250) This issue also contained the back-up story, "What if the Man-Thing had regained Ted Sallis' brain?" (based on Man-Thing (vol. 2) #1) What if Jean Grey had not died? (based on X-Men #137) Reprinted in The Best of What If? Redone in What If? (vol. 2) #32-33. What if Daredevil became an agent of S.H.I.E.L.D.? (based on Daredevil #1) Reprinted in The Best of What If? This also contained the back-up story, "What if the Ghost Rider had been separated from Johnny Blaze?" What if the Avengers defeated everybody? (based on Avengers Special #2) This world was designated Earth-8110 in The Official Handbook of the Marvel Universe: Alternate Universes 2005. This also contained the backup story, "What if Namor had never regained his memories?" What if Spider-Man's clone had lived? (based on The Amazing Spider-Man #149) It was revealed years later that the clone had indeed lived, but had just been in hiding. He was reintroduced under the name Ben Reilly. What if Wolverine had killed the Hulk? (based on The Incredible Hulk #181) The concept was reversed in What If? (vol. 2) #50 (although it followed a later rematch between the characters). This issue also includes "What if the Fantastic Four had never been?" (based on The Fantastic Four #1). The latter world was designated Earth-8222 in Marvel Encyclopedia: Fantastic Four. What if the Avengers had become pawns of Korvac? (based on Avengers #177) Reprinted in The Best of What If? Extended in #43. A version of this world was visited by Quasar in Quasar #30. What if the Dazzler had become the herald of Galactus? (based on Dazzler #11) / What if Iron Man was trapped in the time of King Arthur? (based on Iron Man #150) What If Humor Issue Parts reprinted in The Best of What If? What if Elektra had lived? (based on Daredevil #182) This issue also includes "What if Hank Pym had died?" (based on Avengers #212) What if the Fantastic Four had not gained their super-powers? (based on The Fantastic Four #1) Reprinted in The Best of What If? This version of the team reappeared in What If? (vol. 2) #39. This world was designated Earth-8212 in Marvel Encyclopedia: Fantastic Four. This issue also includes "What if Richard Rider had not lost the power of Nova?" (based on Nova #25) What if the Thing and the Beast continued to mutate? (based on Marvel Two-in-One #81 and Amazing Adventures #11) The world featuring the Thing was designated Earth-8321 in Marvel Encyclopedia: Fantastic Four. This issue also includes "What if the Silver Surfer had lost the Power Cosmic?" (based on Fantastic Four #50) What if... featuring Daredevil (set in a possible future) and Captain America (based on Captain America #237) Three alternate futures, including a Vision and Scarlet Witch tale. Only one diverges from a specific point: the Captain America story "What if Sharon Carter had not died?" What if Thor battled Conan the Barbarian? What if Doctor Strange had not become Master of the Mystic Arts? (based on Strange Tales #110) This timeline made a cameo appearance in Paradise X. What if the Sub-Mariner had saved Atlantis from its destiny? (based on Sub-Mariner #1) What if the Invisible Girl had died in childbirth? (based on Fantastic Four Annual #6) This world was designated Earth-8312 in Marvel Encyclopedia: Fantastic Four. What if Conan the Barbarian was stranded in the 20th century? An alternate ending to What If? #13. Also includes an extended ending to What If? #32. What if Captain America were revived today? (1983) (based on Avengers #4) Redone in What If? (vol. 2) #67-68 and 103. What if the Hulk went berserk? (based on The Incredible Hulk #1) What if Spider-Man's Uncle Ben had lived (and Aunt May was murdered instead)? (based on Amazing Fantasy #15) Redone in What If Spider-Man (2005) What if Loki had found the hammer of Thor? (based on Journey into Mystery #83) Final issue of the original series.
Select stories (noted above) were collected in a trade paperback, The Best of What If, in 1991. The entire series was collected in a series of seven volumes titled What If Classic from 2004 to 2010, with the exception of issues #13 and 16 and the lead story of #43 because they featured licensed characters, namely Conan the Barbarian and Fu Manchu.
Special (1988) What if Iron Man had been a traitor? (based on Tales of Suspense #39)
Volume 2 (1989–1998) What if the Avengers had lost the Evolutionary War? (based on Avengers Annual #17) Visited by Quasar in Quasar #30. What if Daredevil had killed the Kingpin? (based on Daredevil #228) What if Steve Rogers had refused to give up being Captain America? (based on Captain America #332) What if the Venom alien costume had possessed Spider-Man? (based on The Amazing Spider-Man #258) Visited by Quasar in Quasar #30. What if the Vision had destroyed the Avengers? (based on Avengers #9) What if the X-Men lost Inferno? (based on The New Mutants #73) What if Wolverine was an agent of S.H.I.E.L.D.? (based on The Incredible Hulk #181) What if Iron Man lost the Armor Wars? (based on Iron Man #225) What if the X-Men died on their first mission? (based on Giant-Size X-Men #1) This world was designated Earth-105709 in Quasar #30. What if the Punisher's family had not been killed? What if the Fantastic Four all had the same power? (based on Fantastic Four #1) The four worlds shown here were designated Earths 9031 through 9034 in Marvel Encyclopedia: Fantastic Four. What if the X-Men had stayed in Asgard? (based on The New Mutants Special Edition #1) What if Professor X of the X-Men had become the Juggernaut? (based on Uncanny X-Men #12) What if Captain Marvel had not died? (based on The Death of Captain Marvel) Visited by Quasar in Quasar #30. What if the Fantastic Four had lost the trial of Galactus? (based on Fantastic Four #262) This world was designated Earth-907 in Marvel Encyclopedia: Fantastic Four. What if Wolverine battled Conan the Barbarian? (based on Uncanny X-Men #137) What if Kraven the Hunter had killed Spider-Man? (based on Web of Spider-Man #31-32) What if the Fantastic Four battled Doctor Doom before they got their powers? This world was designated Earth-9011 in Marvel Encyclopedia: Fantastic Four. What if the Vision of the Avengers conquered the world? (based on Avengers #254) Two takes, one of which (a utopian world) was revisited in What If? (vol. 2) #36. The utopian world was designated Earth-90110 and the dystopian world Earth-90111 in The Official Handbook of the Marvel Universe: Alternate Universes 2005.