Charles Xavier

* Absorbing Man - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Alicia Masters - Charles is involved in a manipulated attack on Alicia and Fantastic Four (FaFo #28), and they meet at the Richards engagement party (#36) and wedding (An. #3)
* Amanda Sefton - they first met at the X-Mansion in An. X-Men #4, X-allies many times since then
* Ancient One - Charles knew of Ancient One from his brother (X-Men #33)
* Angel - founders of X-Men (#1-94, again from #375)
* Ant-Man - many team crossovers (since X-Men #9)
* Apocalypse - *Enemy*: Charles and Cable discuss Apocalypse telepathically (X-Force #16), later adversaries in the Apocalypse Twelve event (X-Men #377-379)
* Arcade - *Enemy:* the X-Men plot against Arcade and Doom in #145
* Artie Maddicks - they meet at the wedding of Jean and Scott (X-Men #2.30)
* Aurora - Nightcrawler mentions Aurora in X-Men #139, they join forces in X-Men/Alpha Flight #1-2
* Avalanche - *Enemy:* their teams fight it out in Days of Future Past (X-Men #141-142)
* Banshee - clashed in X-Men #28 but later X-Men (#94-111) and always allies
* Baron von Strucker - *Enemy:* they had a battle in Israel after the war (backstory in X-Men #161)
* Beast - founders of X-Men (#1-66, also from #375)
* Bishop - members of X-Men (#287-379)
* Black Panther - Avengers and X-Men battle but then join forces against the mind-control of Magneto (Avengers #110-111)
* Black Widow - Avengers and X-Men battle but then join forces against the mind-control of Magneto (A #111), later Charles is the possessed opponent for Avengers in Onslaught (e.g. X-Men #2.55)
* Blob - *Enemy:* classic foe of the X-men (from #3)
* Boom-Boom - X-Men and X-Force clash in X-Cutioner's Song (U X-Men #295), but later X-Force move into the mansion (from XF #44)
* Bulldozer - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Cable - first hears of baby Nathan from Illyana (New Mutants #50), later allies in Genosha (U X-Men #272), X-Force move into the mansion (from XF #44), finally members of X-Men (#375-379)
* Caliban - *Ally*: both were in the Alley in X-Men #179, they join forces to end the spell that Kulan Gath put on New York (#191), and X-Force reside in the mansion (from XF #44) - *Enemy*: adversaries in the Apocalypse Twelve event (X-Men #377-379)
* Callisto - *Enemy:* the X-Men confront Callisto in the Alley (X-Men #179), and she later again attacks (#293) - *Ally:* they join forces to end the spell that Kulan Gath put on New York (#191), and Callisto saves him after a brutal assault (#193), later both members of the Genosha Excalibur (from #3.2)
* Cannonball - Charles fathered the New Mutants (#1-30), and they are also X-men together (from X-Force #44)
* Captain America - many team crossovers since X-Men #9
* Captain Britain - Charles sees a glimpse of him (Excalibur #17)
* Carol Danvers - Carol stayed with the X-Men in the period around the original Brood saga (#150-171), and they journey together with the Starjammers (from #201)
* Celeste Cuckoo - residents of the mansion at the same time (from before X-Men #409)
* Chamber - X-Men at the same time but in different teams (X-Men #409-423)
* Ch'od - first met when they both were with the X-Men in the Bermuda Sea (#158-161), later they journey together on the Starjammer (from #201)
* Cloak - Charles helped resolve the conflict between C&D and New Mutants (#24-25)
* Colossus - core X-Men (#94-200, #375-390)
* Corsair - they join forces in the original Brood saga (X-Men #155-163), later they journey together with the Starjammers (from #201)
* Crystal - they meet at the wedding of Jean and Scott (X-Men #2.30) and Charles is the possessed opponent for Avengers in Onslaught (e.g. X-Men #2.55)
* Cyclops - founders of X-Men (#1-200, also from #375)
* Dagger - Charles helped resolve the conflict between C&D and New Mutants (#24-25)
* Daredevil - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3), and Daredevil battles and frees X-Men from the mind-control of Magneto (Avengers #111)
* Dazzler - join forces against Hellfire Club (X-Men #131), in Mojoverse (#2.10) and Genosha (#392-393)
* Doctor Doom - *Enemy:* the X-Men plot against Arcade and Doom in #145, and they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Doctor Octopus - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Doctor Strange - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3), allies many times (Since X-Men #33)
* Domino - they meet at the wedding of Jean and Scott (X-Men #2.30), join forces in Israel (#2.40), and X-Force move into the mansion (from XF #44)
* Doug Ramsey - Doug becomes friends with the X-Men since New Mutants #14, and under the tutelage of Xavier as NM member (#21-30)
* Edwin Jarvis - they meet when X-Men seek help from the Avengers in X-Men #155
* Emma Frost - *Enemy:* iconic foe of the Dark Phoenix years (X-Men #129) - *Ally:* they have to join forces in U X-Men #281-282, later cooperate around the institutes, even X-Men at the same time but in different teams (from before X-Men #409)
* Enchantress - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Firelord - Firelord attacks the X-Men in #105-106
* Firestar - their two teams do battle at NORAD (X-Men #193)
* Foggy Nelson - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3)
* Forge - he first talks about Forge in X-Men #192, later X-Men members together (from #277)
* Franklin Richards - they first meet at the X-Mansion in Ann. X-Men #5, later Charles holds him hostage in Onslaught
* Frenzy - she joins the X-Men in liberating Charles from Genosha (U X-Men #392-393)
* Galactus - *Enemy*: the X-Men see an illusion of Galactus in their back yard (XM An. #7), they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series), and they have a confrontation on the Skrull homeworld (X-Men #370)
* Gambit - X-Men members together (#277-379)
* General Ross - they work together to contain Hulk in suspension in a lab (Avengers #88)
* Gladiator - they must have met already when Charles first resided with the Xi'ar, and then in X-Men #137 and several times later on
* Glenn Talbot - they work together to contain Hulk in suspension in a lab (Avengers #88)
* Glob Herman - both residents at the X-Mansion, where the kids in Omega Gang assault the professor (New X-Men #136)
* Guardian - Charles brings word of the death of Hudson (Kitty Pryde & Wolverine #4), they work together in Westchester as they study Wolverine's physiology (W #91-95), but they clash over custody of the boy Sammy Paré (X-Men #422)
* Havok - members of X-Men (from #65-94)
* Hawkeye - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3), allies on Beyonder's Battleworld planet (first Secret Wars series). later Charles is the possessed opponent for Avengers in Onslaught (e.g. X-Men #2.55)
* Henry Gyrich - *Enemy:* Gyrich was persecuting his first group of New Mutants (from #1) - *Ally:* they join forces in Bloodties (X-Men #2.26)
* Hepzibah - first met when they both were with the X-Men in the Bermuda Sea (#158-161), later they journey together on the Starjammer (from #201)
* Hulk - first hears of Hulk from Iron-Man (Avengers #3), the X-Men also discuss Hulk (XM #66), later Charles helps with containing Hulk in suspension in a lab (A #88), but they are allies on Beyonder's Battleworld planet (first Secret Wars series)
* Human Torch - first Charles influenced the battle against Mad Thinker's android (Fantastic Four #28), then they meet at State University (#35) and the Richards engagement party (#36)
* Husk - she came to Xavier for guidance (mentioned in X-Force #42), later both residing at the X-Mansion (from around X-Men #410)
* Iceman - founders of X-Men (#1-94, also from 377)
* Iron Fist - Charles overhears Misty Knight talking with Iron Fist in X-Men #118
* Iron-Man - many team crossovers (since Tales of Suspense #49)
* J. Jonah Jameson - Charles reads his newspaper column in Marvel Team-up #4
* Jean Grey - they met when she was young (retcon of Bizarre Adventures #27 and X-Men #-1). Original X-Men (#1-137, also from #375). Co-telepath and often his closest confidante in the team ever since he secretly trained her in telepathy (#40). Early on he had forbidden feelings for her (#3)
* Jubilee - X-Men members together (#277-379 and from #427)
* Juggernaut - step-brother and foe, later both residing at the X-Mansion (from X-Men #413)
* Julia Carpenter - they are allies on Beyonder's Battleworld planet (first Secret Wars series)
* Kang - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Karen Page - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3)
* Karma - Charles first heard of Karma from Moira (X-Men #165), and proceeded to create the New Mutants (Graphic Novel #4 - NM#6)
* Ka-Zar - the X-Men and Charles discuss Ka-Zar (X-Men #10), later they communicate in Savage Land (XM An. #7)
* Kid Omega - residents at the X-Mansion, where the kids in Omega Gang assault the professor (New X-Men #136)
* Klaw - they are on opposite sides on Beyonder's Battleworld planet (first Secret Wars series)
* Kraven the Hunter - Charles is attacked by a skrull version on the skrull homeworld (X-Men #370)
* Leech - both were in the Alley in X-Men #179, maybe did not exactly meet then, but did meet at the wedding of Jean and Scott (#2.30)
* Lilandra - first has dreams of her struggles in X-Men #97, becomes life partner since they first meet (#105), and fellow Starjammers (from #201). Nickname: "My Love" (New Mutants #13)
* Lizard - Charles reads Spider-Man's memories about Lizard in Marvel Team-Up #4, later they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Loki - they clash in the "Loki's gift" adventure in Canada (X-Men/Alpha Flight #1-2)
* Longshot - they join forces in Mojoverse in X-Men #2.10
* Luna Maximoff - the X-Men work to save Luna in Bloodties (X-Men #2.26)
* Madelyne Pryor - they met at the weddings of Wolverine and Mariko (X-Men #173), Madelyne and Scott (#175)
* Mad Thinker - *Enemy:* Mad Thinker and Puppet Master manipulate X-Men and Fantastic Four to fight each other (FaFo #28)
* Magik - first met at the Soviet kolkhos (GSX#1), later both residents of the X-mansion (X-Men #148-200). Nickname: "Young Lady" (New Mutants #51)
* Magma - she becomes member of his New Mutants (#13-30)
* Magneto - *Ally:* first met as youths in Israel (backstory), allies again since Magneto first came to live with the X-Men (from #196), later members of the Genosha Excalibur (from #3.2) - *Enemy:*archenemy since X-Men #1. Nickname: "My Friend" (#200)
* Mandarin - *Enemy:* Charles knows that Psylocke has a past with Mandarin (X-Men #2.32)
* Marrow - in X-Men together (#375-379)
* Mastermind - *Enemy:* classic foe of the X-Men (ever since #4)
* Meggan - Charles sees a glimpse of her (Excalibur #17)
* Mindee Cuckoo - appear to residents of the mansion at the same time (around X-Men #409)
* Mirage - he tutored the New Mutants (#1-30)
* Mister Sinister - Charles and Cable discuss Sinister telepathically (X-Force #16)
* Misty Knight - befriended through Jean Grey (X-Men #102)
* Moira MacTaggart - lifelong colleague and partner, as they met in Oxford as young (X-Men #389[retcon]). He names her as "My best friend" (Excalibur #101)
* Mole Man - *Enemy*: X-Men battle Mole Man in the Baxter Building (Fantastic Four An. #3) and in the underground realms (X-Men #34)
* Monet - the X-Men save Monet from Cassidy keep in Scotland (#412)
* Monica Rambeau - they are allies on Beyonder's Battleworld planet (first Secret Wars series)
* Morbius - *Enemy:* they battle over Spider-Man in Marvel Team-up #4
* Multiple Man - often together on Muir Island (e.g. New Mutants #26-28, X-Men #280) and X-Cutioner's Song (#295)
* Mystique - *Enemy:* their teams fight it out in Days of Future Past (X-Men #141-142) and later - *Ally:* Mystique did her part in the Muir Island Saga (X-Factor #69), and she works secretly for Charles (Mystique mini-series)
* Nick Fury - they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3), X-Men and SHIELD join forces in X-Men #2.2-3, and they both serve in the Commission on Superhuman Activities (X-Force #27-28)
* Nightcrawler - core X-Men (#94-200, also from #375)
* Northstar - they are both involved in Loki's Gift in Canada (X-Men/Alpha Flight #1-2), and Northstar joins the X-Men in liberating Charles from Genosha (X-Men #392-393), finally members of X-Men (from #414)
* Nova - *Enemy*: Doctor Doom talks of Galactus being found by Nova (Secret Wars #11), and they have a confrontation on the Skrull homeworld (X-Men #370)
* Nova (Richard Rider) - Charles heard that Nova stole a Quinjet (mentioned in New Warriors #31)
* Phoebe Cuckoo - appear to residents of the mansion at the same time (around X-Men #409)
* Piledriver - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Polaris - members of X-Men (from #65-94, also from #377)
* Psylocke - X-Men members together (#277-379)
* Puck - they are both involved in Loki's Gift in Canada (X-Men/Alpha Flight #1-2), later they clash at the Xavier Institute over custody of the boy Sammy Paré (X-Men #422)
* Puppet Master - *Enemy:* Mad Thinker and Puppet Master manipulate X-Men and Fantastic Four to fight each other (FaFo #28), later they battle again (XM #27)
* Pyro - *Enemy:* their teams fight it out in Days of Future Past (X-Men #141-142)
* Quicksilver - many collaborations and clashes (since X-Men #4)
* Rachel Summers - she is a resident at the mansion (from X-Men #184), and both X-Men (#188-200)
* Raza - first met when they both were with the X-Men in the Bermuda Sea (#158-161), later they journey together on the Starjammer (from #201)
* Reed Richards - first Charles influenced the battle against Mad Thinker's android (Fantastic Four #28), then they meet at State University (#35) and the Richards engagement party (#36)
* Rictor - X-Men and X-Force clash in X-Cutioner's Song (U X-Men #295), and they also meet in the X-mansion (X-Force #44)
* Rick Jones - they meet at the Richards engagement party (Fantastic Four #36)
* Rogue - *Enemy:* first becomes aware of Rogue's misdeeds in Avengers An. #10 - *Ally:* in X-Men together (#171-200, also #375-379)
* Sabretooth - *Enemy:* first hears Wolverine talk of Sabretooth (Woverine #50), later X-Men hold him captured at the mansion (X-Men #2.33)
* Sasquatch - they are both involved in Loki's Gift in Canada (X-Men/Alpha Flight #1-2), later they clash at the Xavier Institute over custody of the boy Sammy Paré (X-Men #422)
* Sauron - Xavier succeeds in curing Lykos in the Westchester mansion (Marvel Fanfare #4)
* Scarlet Witch - many encounters through the years (since X-Men #4)
* Sebastian Shaw - *Enemy:* iconic foe of the Dark Phoenix years (since X-Men #129)
* Selene - *Enemy:* they battle over Rachel Summers and later (X-Men #184-191)
* Shadowcat - X-Men together (#129-200, #375-390)
* Shaman - they are both involved in Loki's Gift in Canada (X-Men/Alpha Flight #1-2)
* Shanna the She-Devil - they meet in the Savage Land because of Impossible Man (X-Men An. #7)
* Shatterstar - X-Men and X-Force clash in X-Cutioner's Song (U X-Men #295), later X-Force move into the mansion (from XF #44)
* She-Hulk - they are allies on Beyonder's Battleworld planet (first Secret Wars series)
* Siryn - they first meet at the X-Mansion in X-Men #148, but they battled in the Saga of Muir Island (U X-Men #280) and in X-Cutioner's Song (#295)
* Snowbird - they are both involved in the "Loki's gift" adventure in Canada (X-Men/Alpha Flight #1-2), later they clash at the Xavier Institute over custody of the boy Sammy Paré (X-Men #422)
* Spider-Man - X-Men first heard of Spidey (An. SM #1), they meet at the wedding of Reed and Susan Richards (Fantastic Four An. #3), some collaborations (e.g. Marvel Team-up #4, X-Men #191)
* Spider-Woman (JD) - JD visited the X-Men (#148) and they work together to solve the tragedy of Carol Danvers (Avengers An. #10)
* Spiral - *Enemy:* Charles gets involved when Spiral attacks the X-Men (#2.31-32)
* Starfox - Charles remembers the battles in the New York created by Kulan Gath (X-Men #191)
* Storm - core X-Men (#94-200, also #375-379), it is later shown that they had a brief encounter when Ororo was a child in Cairo (New Mutants #34)
* Strong Guy - Guido joins forces with the X-Men several times (U X-Men #278-295)
* Sub-Mariner - Namor met the X-Men on Magneto's island (X-Men #6)
* Sunfire - they join forces several times since Krakoa (GSX#1, X-Men #181, #284)
* Sunspot - Charles tutored the New Mutants (#1-30), later X-Force live in the mansion (from XF #44)
* Susan Richards - first Charles influenced the battle against Mad Thinker's android (Fantastic Four #28), then they meet at State University (#35) and the Richards engagement party (#36)
* Talisman - they are both involved in the "Loki's gift" adventure in Canada (X-Men/Alpha Flight #1-2)
* Tessa - *Ally:* Charles and New Mutants liberate Tessa from Donald Pierce (Graphic Novel #4), later they meet at the Xavier Institute (X-Treme X-Men #23) - *Enemy:* they come head to head in the Hellfire Club (X-Men #189)
* The Thing - first Charles influenced the battle against Mad Thinker's android (Fantastic Four #28), then they meet at State University (#35) and the Richards engagement party (#36)
* The Watcher - Lilandra relays the message of The Watchers to the X-Men (#2.40)
* Thor - many team crossovers (since X-Men #9)
* Thunderball - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* Tigra - they join forces against Deathbird in X-Men #155
* Titania - they are on opposite sides on Beyonder's Battleworld planet (first Secret Wars series)
* Toad - *Enemy:* classic foe of the X-Men (from #4)
* Trish Tilby - Charles and Hank talk about Trish in X-Men #2.26, and she visits the mansion (#2.70)
* U. S. Agent - they join forces in Bloodties (X-Men #2.26)
* Valerie Cooper - Charles believes he works with Cooper to rescue Muir Island (X-Factor #69), later they join forces in X-Cutioner's Song (U X-Men #295) and on the Commission on Superhuman Activities (X-Force #24-28)
* Vanisher - *Enemy:* classic foe of the X-men (from #2)
* Vindicator - they are both involved in the "Loki's gift" adventure in Canada (X-Men/Alpha Flight #1-2), and work together in Westchester as they study Wolverine's physiology (W #91-95), but clash over custody of the boy Sammy Paré (X-Men #422)
* Viper - *Enemy:* Viper waged war on Charles and the New Mutants early on (#5-6)
* Vision - Avengers and X-Men battle but then join forces against the mind-control of Magneto (A #111), Charles also remembers the battles in the New York created by Kulan Gath (X-Men #191), later Charles is the possessed opponent for Avengers in Onslaught (#2.55)
* Warlock - Charles was leader of New Mutants (from #21-30)
* War Machine - they are allies on Beyonder's Battleworld planet (first Secret Wars series)
* Warpath - they first battle at NORAD (X-Men #193), as well as in X-Cutioner's Song (#295) but later Charles helps him (#2.17), and then X-Force move into the mansion (from XF #44)
* Wasp - many team crossovers since X-Men #9
* Wolfsbane - Charles created the New Mutants (#1-30)
* Wolverine - core X-Men (#94-200, also from #375)
* Wrecker - they are on opposite teams on Beyonder's Battleworld planet (first Secret Wars series)
* X-Man - Scott and Charles talk about Nate (X-Men Unlimited #25), then both briefly X-Men (#375-379)