NOTE: The format below is most likely NOT how this article will eventually look. Instead, much like the idea itself this will be a work-in-progress.
The joke goes, “If a person who speaks three languages is a trilingual, and someone who speaks two languages is bilingual… what do you call someone who speaks only one?” The answer: an American.
Since a majority of the characters in the Marvel Universe are from the United States, it comes as no surprise that almost all of the characters speak English. However, some of them are not only from other countries, but some of the American heroes and villains are actually multi-lingual. Unless otherwise stated, it is assumed that the characters below speak English, so the languages listed next to them are any other languages that they speak.
Bi-lingual by Character
Angel Real Name: Warren Kenneth Worthington III
Languages:
Spanish [Uncanny X-Men #504]
Armor Real Name: Hisako Ichiki
Languages:
Japanese [Astonishing X-Men (3rd series) #13]
Aurora Real Name: Jeanne Marie Beaubier
Languages:
French (raised French-Canadian)
Beast Real Name: Hank McCoy
Languages:
French:
Latin:
Japanese [X-Men (2nd series) #21-22]
Pashto (mispelled as "pushti") [X-Men Annual (2nd series) #1]
Russian
Spanish [Uncanny X-Men #504]
Brand, Special Agent Real Name: Abigail Brand
Languages:
Kree (multiple dialects fluently) [Secret Invasion #5]
Skrull (limited vocal ability) [Secret Invasion #5]
Multiple unrevealed non-Terran languages [Giant-Sized Astonishing X-Men #1]
Cable Real Name: Nathan Christopher Charles Summers
Languages:
Askani (raised in Askani future)
Cerise Real Name: Cerise
Languages:
Shi’ar (raised in Shi’ar Empire)
Cheney, Lila Real Name: Lila Cheney
Languages:
Skrull (source?)
Shi’ar (source?)
Colossus Real Name: Piotr Nicoleivitch Rasputin
Languages:
Russian (raised in Russia)
Cyclops Real Name: Scott Summers
Languages:
Mandarin Chinese* (telepathically taught by Emma Frost) [New X-Men Annual 2001] - possibly temporary
Russian [Uncanny X-Men #153] (telepathically taught by Xavier)
Daken Real Name: Akihiro
Languages:
German (inferred)[Wolverine: Origins #11-12]
Greek [Wolverine: Origins #26]
Japanese [Wolverine: Origins #26]
Darkstar Real Name: Laynia Petrovna
Languages:
Russian (raised in Russia)
Darwin Real Name: Armando Munoz
Languages:
Shi'ar [Uncanny X-Men #478]
*theoretically, Darwin's power makes him omni-lingual
Empath Real Name: Manuel Alfonso Rodrigo de la Rocha
Languages:
Spanish (Castilian) [Raised in Spain]
Fantomex Real Name: unknown
Languages:
French
Feral Real Name: Maria Callasantos
Languages:
Spanish (source?)
Emma Frost Real Name: Emma Frost
Languages:
Mandarin Chinese* (telepathically self-taught) [New X-Men Annual 2001]
Gambit Real Name: Remy LeBeau
Languages:
French (raised in New Orleans French quarter)
Karma Real Name: Xi’An Coy Manh
Languages:
French
Vietnamese (raised in Vietnam)
M II Real Name: Monet Yvette Clarisse Maria Therese St. Croix
Languages:
French [X-Factor (3rd series) #15]
Maggott Real Name: Japheth
Languages:
Afrikaan (raised in South Africa)
Magik I Real Name: Illyana Rasputin
Languages:
Russian (raised in Russia)
Magik II / Daytripper Real Name: Amanda Sefton
Languages:
German (raised in Germany)
Magma Real Name: Amara Aquilla
Languages:
Latin (raised in Nova Roma)
Magneto Real Name: Magnus
Languages:
French [Classic X-Men #12]
German [X-Men: Magneto Testament LS]
Russian [Uncanny X-Men #150]
Ukrainian [Classic X-Men #12] (presumed, language not referenced, but was in Ukrainian village
Ms. Marvel Real Name: Carol Danvers
Languages:
Kree
Arabic [Ms. Marvel (2nd series) #30]
Russian [Before the Four: Ben Grimm & Logan LS]
Multiple Man Real Name: Jamie Madrox
Languages:
French [X-Factor (3rd series) #43]
Hawaiian [Madrox #3]
Russian [Madrox #3]
Mystique Real Name: Raven Darkholme
Languages:
French
German
Korean [Mystique #7]
Portuguese (Brazilian) [Mystique #13]
Spanish [Mystique #1-6]
Does not speak: Afrikaan [Mystique #8]
Notes: Mystique claims to speak 11 languages fluently [Mystique #8]. Presumably this would be 10, not counting English.
Nightcrawler Real Name: Kurt Wagner
Languages:
German (raised in Germany)
Russian [Uncanny X-Men #153] (telepathically taught by Xavier)
Spanish [X-Men: Divided We Stand #1]
Northstar Real Name: Jean-Paul Beaubier
Languages:
French (raised French-Canadian)
Professor X Real Name: Charles Francis Xavier
Languages:
German [Uncanny X-Men #161]
Mikael Rasuptin Real Name: Mikhail Rasputin
Languages:
Russian (raised in Russia)
Renascence Real Name: Sofia Mantega
Languages:
Spanish (raised in Venezuela) [New Mutants (2nd series) #1]
Revanche Real Name: Kwannon
Languages:
Japanese (raised in Japan)[X-Men (2nd series) #22]
Dr. Cecilia Reyes Real Name: Cecilia Reyes
Languages:
Spanish
Rictor Real Name: Julio Richter
Languages:
Spanish [X-Force Annual ‘99]
Rogue Real Name: Anna Marie
Languages:
French
Sabra Real Name: Ruth Bat-Seraph
Languages:
Hebrew (modern) – (raised in Israel)
Sasquatch I Real Name: Walter Langkowski
Languages:
French [Alpha Flight (1st series) #108]
German [Alpha Flight (1st series) #108]
Selene Real Name: Selene
Languages:
Latin [New Mutants (1st series) #9]
Shadowcat Real Name: Katherine “Kitty” Pryde
Languages:
Hebrew
Japanese [Kitty Pryde & Wolverine] (earlier?!?)
Russian [Uncanny X-Men #153, 160]
Skrull [X-Men (2nd series) #90, 95 & 96, Uncanny X-Men #376]
Shatterstar Real Name: Benjamin Russel
Languages:
Spanish [X-Force Annual ‘99]
Silver Samurai Real Name: Kenuichio Harada
Languages:
Japanese (raised in Japan)
Skin Real Name: Angelo Espinosa
Languages:
Spanish (raised in Latin area of Los Angeles)
Storm Real Name: Ororo Munroe
Languages:
Arabic (presumably, raised in Egypt)
Russian [Uncanny X-Men #153] (telepathically taught by Xavier)
Sunfire Real Name: Shiro Yoshida
Languages:
Japanese (raised in Japan)
Sunpyre Real Name: Leyu Yoshida
Languages:
Japanese (raised in Japan)
Sunspot Real Name: Roberto “Bobby” DaCosta
Languages:
Portuguese (Brazilian) – (raised in Brazil)
Latin (non-proficient) [X-Treme X-Men #34]
Askani [X-Force (1st series) #47, 50]
Surge Real Name: Noriko Ashida
Languages:
Japanese [New X-Men (2nd series) #7]
Takiguchi, Yuriko Real Name: Yuriko Takiguchi
Languages:
Japanese [Uncanny X-Men #506]
Russian [Uncanny X-Men #506]
Tarot Real Name: Marie-Ange Colbert
Languages:
French (raised in France)
Thorn Real Name: Lucia Callasantos
Languages:
Spanish (verification?)
Thunderbird III Real Name: Neal Shaaara
Languages:
Hindi? (raised in India)
Wolverine Real Name: “Logan” / James Howlett
Languages:
Farsi [Wolverine: Origins #32]
German [Wolverine: Origins #8]
Japanese [X-Men (1st series) #118]
Korean [Rampaging Wolverine #1]
Mandarin Chinese [New X-Men Annual 2001]
Pashto (mispelled as "pushti") [inferred, X-Men Annual (2nd series) #1]
Russian [Uncanny X-Men #153] (telepathically taught by Xavier)
Thai [Wolverine: Dangerous Games #1]
Vietnamese (though it’s “rusty”) [Wolverine (2nd series) #4]
Doopspeak [X-Force (1st series) #120]
Mariko Yashida Real Name: Mariko Yashida
Languages:
Japanese (raised in Japan)
Yuko Real Name: unknown
Languages:
Japanese (raised in Japan)
X-Man Real Name: Nate Grey
Languages:
German [X-Man: All Saints Day]
Xorn I Real Name: unkown
Languages:
Mandarin Chinese* (raised in China)
Xorn II Real Name: Shen Xorn
Languages:
Mandarin Chinese* (raised in China)
Bi-lingual by Language
Afrikaan: Maggott
Arabic: Storm
Chinese: Cyclops, Emma Frost, Xorn I, Xorn II
French: Aurora, Fantomex, Gambit, La Nuit, Northstar, Rogue, Northstar
German: Mystique, Nightcrawler, Professor X
Hawaiian: Multiple Man
Hebrew: Kitty?, Sabra
Hindi: Thunderbird III
Japanese: Beast, Sunfire, Sunpyre, Wolverine, Mariko, Silver Samurai, Yashida, Yuko,
(Banshee, Colossus, Cyclops, Storm,
Latin: Beast, Magma,
Portuguese (Brazilian): Mystique, Sunspot
Russian: Colossus, Darkstar, Magik I, Multiple Man, Mikael Rasuptin, Shadowcat
Spanish: Mystique, Dr. Cecilia Reyes, Rictor, Saint Anna, Shatterstar, Skin
Vietnamese: Karma, Wolverine (partial)
Fictional languages
Askani: Cable, Rictor
Doopspeak: Anarchist, Coach, Dead Girl, Doop, El Guapo, Mr. Sensitive, Phat, U-Go Girl, Venus Dee Milo, Vivisector, Wolverine, Zeitgeist
Kree: Ms. Marvel
Skrull: Professor X, Shadowcat
Shi’ar: Cerise, Professor X