BEWARE OF SPOILERS!
- Brought to You by the Letter "S": Or "L", as seen in the middle of the Legion ring.
- Chekhov's Gunman: Their existence was first alluded to when Kara sees a Legion ring when she visits the Fortress of Solitude for the first time. There's also a glimpse of the aforementioned moment when Barry Allen first travels to Earth-2, but Supergirl is yet to be integrated into the Arrowverse at the time.
- Comic-Book Movies Don't Use Codenames: Downplayed. The group are only referred to as "The Legion" instead of their full title from the comicbooks.
- The Ghost: Only Mon-El, Imra, and Brainy appeared from the original lineup as the rest are sick due to the Blight.
- Movie Superheroes Wear Black: In the comicbooks they wear colorful costumes. Here, they wear mostly black leather, and while Mon-El eventually wears his canonical costume, it's notably muted.
- Ring of Power: Their main arsenal. The rings provide many powers such as Time Travel and Flight.
- Time Travel: They came from the 31st century to stop the Blight in The Present Day.
Known Aliases: Mike Matthews
Portrayed By: Chris Wood
Voiced By: Jaime Alberto Carrillo (Latin-American Spanish dub), Kazuyuki Okitsu (Japanese dub)
Appearances: Supergirl | The Flash | Crisis on Earth-X noteA Daxamite Prince stranded on Earth.
- Absence Makes the Heart Go Yonder: When Mon-El first arrived in the thirty-first century, the only thing he could focus on was getting back to Kara. According to his wife Imra, he wouldn't look at another woman for years. He only moved on when he finally realized there was no way back to his First Love. Then it turned out there was a way back, but the Legion deliberately kept him in the dark about it.
- Achilles' Heel: In the comics, lead is to Mon-El what Kryptonite is to Superman and Supergirl, forcing the character to take regular injections to counteract the fact there is lead everywhere on Earth. The TV version also shares this aversion to lead, but it is severely downplayed and there's been no indication of him suffering ill effects on Earth.
- Adaptation Name Change: While in the comics the character has used the name "Mon-El" it was always an alias but not his real name, instead his real name was "Lar Gand". It is later revealed that he's a Decomposite Character, with his father using the latter name.
- Adaptational Wimp: At least compared to comic Mon-El, who is basically a Superman whose Kryptonite Factor (and Weaksauce Weakness) is lead. Here, he has the same limited powers of the original Superman from Action Comics, including Super Strength, Super Toughness, Super Speed, and In a Single Bound. The last ability is Lampshaded and mocked by Mr. Mxyzptlk. He can fly, but only because of the Legion ring.
- Adaptation-Induced Plot Hole: In the comics, "Mon-El" was a name given to him by a young Clark, who assumed they must be brothers. Here it's his real name, and the fact that he has the same surname as Superman and Supergirl is apparently a complete coincidence that not one person remarks on.
- Adorkable: On Earth, due to being a Fish out of Water, and he is on the same levels as Kara.
- Alliterative Name: His alias, Mike Matthews.
- Ambiguously Bi: He's only shown attraction to women, but upon learning that Alex and Maggie are a couple, he casually notes that Daxam had a very free-thinking view on that kind of thing, describing it as, "The more, the merrier."
- And Starring: In the series OBB starting with Season Two, replacing the departing Calista Flockhart (Cat Grant).
- Badass Beard: He's got one after his return from the future.
- Badass Cape: Part of his new costume. Can use his cape to seize and throw opponents with incredible effectiveness.
- Brought Down to Normal: Like Kara, a red sun robs him of his Daxamite powers.
- Brutal Honesty: Combined with Cannot Tell a Lie. Mon-El has a horrible sense of tact.
- But Now I Must Go: After the Season 3 finale, he is forced to leave Kara's side again, due to the future still being in danger.]
- Category Traitor: The Daxamite soldiers don't hide their hatred for their treacherous prince.
- Character Development: Season Two follows his journey from a good-natured yet indifferent playboy to a genuinely selfless superhero.
- Comic-Book Movies Don't Use Codenames: Mon-El has not been referred to as "Valor" yet, likely because he is still in the process of becoming a full-blown superhero.
- Decomposite Character: In the comics, his real name is Lar Gand. Here, Lar Gand is Mon-El's father.
- Defector from Decadence: Tells his parents he is disgusted by the royal family's exploitation of the people.
- Deuteragonist: Of Season Two.
- Did Not Get the Girl: Ironically, he ends up with neither Imra nor Kara at the end of Season 3, due to his duties as a Legionaire.
- Female Gaze: It's not uncommon that a woman will be ogling his assests.
- First Love: Kara is the first woman Mon-El has ever had a serious relationship with, and the only one he has ever truly loved.
- Fish out of Temporal Water: Twice. First was when he's stuck in the Phantom Zone for thirty seven years immediately after Daxam gets caught with Krypton's explosion. Second when he's accidentally warped into the 31st Century after leaving Earth so he won't be poisoned by Lead.
- Flying Brick: Averted. While Mon-El has most of the same powers as Kara and Clark, he can't fly...but he can "leap tall buildings in a single bound."
- Forgot About His Powers: Invoked regularly. Although several episodes clearly indicate that there's a reason for him not getting directly involved in missions early on, and those he does take part in do not always end well, there are still occasions (such as the "Invasion" crossover arc and moments when Kara is incapacitated or unavailable) where having access to someone who, in theory, is supposed to be almost as powerful as Supergirl and Superman would come in useful, but the DEO doesn't bother.
- Heroic Sacrifice: When Daxam invades Earth, and no other choice is present, he urges Kara with a stiff nod to activate Lena's failsafe weapon and release the toxic lead into the atmosphere, with the implication that it would kill him. Even beforehand, he outright admits he is willing to die if it means saving his friends from his mother. Kara of course is able to get him off Earth in time, yet it's a far cry from the selfish sex hound he was previously.
- Human Aliens: Much like Kryptonians and Titanians, Daxamites don't look different from humans.
- I Choose to Stay: He refuses to go with his parents to return to Daxam and restore its society, obviously to be with Kara.
- Innocent Bigot: While it's clear he means well, Mon-El comes from a very misogynistic race of bullies and hedonsists, and it really shows despite his claims to be learning better.
- I Just Want to Be Special: Essentially, why he asks Kara to train him into becoming a superhero at the end of Supergirl Lives.
- Iconic Outfit: He finally has his red suit with a blue cape in Season 3.
- Jerk with a Heart of Gold: More so from his status as an alien prince; he can be slightly insensitive, and indeed initially very selfish, but none of his actions are ever stirred by ill-intentions.
- King Incognito: He's actually the prince of Daxam.
- Lady Killer In Love: On Daxam he was a raging party animal who took many a female to bed with no feeling whatsoever." On Earth, while his good looks do gather the attentions of the opposite sex (mainly Eve) but here he only has eyes for Kara.
- Last Episode, New Character: Played with. He is the one inside the Kryptonian escape pod seen in the Season One finale, but his proper appearance only happens in the Season Two premiere and his official introduction happens two episodes later.
- Last of His Kind: Mon-El learns from Supergirl that while Daxam wasn't destroyed by Krypton's destruction, it was rendered uninhabitable by the planet's debris. It's later averted when other Daxamites are found to have survived, including his parents.
- Lovable Sex Maniac: He attributes it to 35 years without getting laid.
- MayDecember Romance: He is chronologically older than both Kara and Eve (the former by at least 15 years, the latter by more or less three decades), but his pod traveling through the "Well of Stars" a place where time stands still, stalled his aging.
- Mr. Fanservice: A much more blantant example than James, with plenty of Shirtless Scenes and being the subject of many a Female Gaze.
- My Species Doth Protest Too Much: Mon-El hints at this when he states he wasn't a fan of slavery on Daxam, which was generally accepted there. Also doesn't argue with Holo-Alura's characterization of his planet as "a race of bullies and hedonists", and says his parents weren't great role models.
- Movie Superheroes Wear Black: In Season Three, his Legion suit is pure black and has no cape, in stark contrast to his famous red suit and blue cape from the comics. However, a promo and BTS photos gave away that he would avert this and don the comics suit later in the season, and indeed he does in 3x15, after Winn fixes it up for him.
- Not Wearing Tights: In Season Two, he fights crime using regular clothes.
- Only Sane Man: Out of all of the people in the DEO and Kara's family, Mon-El is the only person to question Jeremiah's return.
- Odd Friendship: Without a doubt Winn became Mon-El's closest friend on Earth, with Winn being his guide to Earth's social scene and pop culture references.
- Pretty Boy: Thoroughly aware of his handsome looks, and often exploits them to his advantage.
- Put on a Bus: At the end of Season Two, he is forced to leave Earth and is subsequently sucked into a space anomaly. This is only temporary, and he returns in the seventh episode of Season Three after a couple of cameos via dreams beforehand. He will not return as a series regular for the fourth season, however.
- Related in the Adaptation: Mon-El and Saturn Girl were never married in the comicbooks.
- Relationship Upgrade: With Kara, starting at the end of 2x13.
- Safety in Indifference: Mon-El's first instinct when he sees someone in trouble is to turn his head and walk away, lest the danger sets its sights on him. Thanks to Kara's influence, he grows out of this.
- Sixth Ranger: Much like Kara, he's an outsourced agent for the DEO on many occasions in their efforts to keep the peace.
- Shirtless Scene: His first battle with Supergirl.
- Spirit Advisor: Appears to a drowning Kara demanding she "wake up" during the submarine attack orchestrated by Morgan Edge.
- Star-Crossed Lovers: Thanks to his mother's machinations and the Daxamite invasion of Earth, Kara has no choice but to infuse the Earth's atmosphere with lead and force all Daxamites off-planet, never to return — including Mon-El. His last words to her before he leaves are to tell her that he loves her and to swear to be the good man she always knew he could be.
- Super Strength: As a result of Daxamite physiology being similar to Kryptonian, he has Super Strength, Super Toughness, Super Speed and Super Jumping while on Earth.
- Tall, Dark, and Snarky: Despite being jailed and confronted by an angry Kryptonian, he maintains a jovial snarky attitude.
- Third-Option Love Interest: Assuming that Winn and James are still in the picture.
- Took a Level in Badass: Did he ever! In the beginning he could only hold his own against Kara and knocked around a lot. After joining the Legion he became more experienced with his powers and can wipe the floor with Kara in sparring.
- Took a Level in Kindness: The guy wasn't ever really nasty, just extremely selfish and shallow, but thanks to Kara's influence he learns to put others before himself, and own up to his faults.
- Useless Boyfriend: He has powers, but after becoming a love interest for Kara and later Imra, he either acts as a bystander or becomes the recipient of the blows.
- Warrior Prince: He's a Superhero in training who also happens to be crown prince of Daxam. Originally averted, as he had to learn combat skills at the DEO.
- Weaksauce Weakness: Like the comic version, lead. Lillian Luthor calls it an "allergy".
- You Are Better Than You Think You Are: Kara believes there is a genuinely noble man under the spoiled Daxam Prince. Due to her influence, she proves herself right.
Imra Ardeen / Saturn Girl
Portrayed By: Amy Jackson
Mon-El's wife from the 31st century and a member of the Legion of Super-Heroes.
- Action Girl: She's an experienced hero, with the fighting skills to match.
- Adaptation Dye-Job: Brunette and green-eyed as opposed to the blonde and blue-eyed version in the comics.
- Aliens of London: Imra's native to Titan, the largest moon of Saturn, but speaks with Amy Jackson's distinctive Manx (Gaelic) accent — being such a weird accent, though, means that it might be an aversion of this trope just by the fact an audience can think it's a fictional one.
- Aloof Dark-Haired Girl: A very graceful dark-haired woman.
- Amicable Exes: What she and Mon-El ultimately end up as.
- Ascended Fangirl: Supergirl was the inspiration for her heroics and she is very excited about meeting her in person.
- Barrier Warrior: She is able to create energy force-fields, using one to protect Mon-El from Reign's freeze breath.
- Composite Character: She has Cosmic Boy's telekinetic abilities, but seemingly lacks her own telepathic abilities. James even asks Mon-El about it, and he claims she's incapable of reading minds.
- Fish out of Water: Being from the 31st century, she experiences a lot of weird things in the present. To her, even such mundane things like eating with her hands are strange.
- Human Aliens: Much like Kryptonians and Daxamites, Titanians don't look different from humans.
- In Name Only: She has very little in common with her comics counterpart thus far, not physically resembling her or even having the same powers.
- Innocently Insensitive: She means well, but her trying to approach Kara about the situation and flirting and kissing around with Mon-El in front of her doesn't help things.
- Mind over Matter: Able to move heavy metallic objects with her mind.
- Movie Superheroes Wear Black: She doesn't wear her bright red and white suit from the comics, instead wearing a mostly black one with maroon on the sides.
- Ms. Fanservice: She's a very beautiful woman; Kara outright compares her to a Greek goddess.
- Nice Girl: So nice that Kara can't even bring herself to hate her, despite being the reason she and Mon-El cannot resume their relationship.
- Related in the Adaptation: Saturn Girl and Mon-El were never married in the comic books; her affections always lay with Lightning Lad, who hasn't shown up or even been mentioned here.
- Second Love: To Mon-El. Or so it seems at first; however, their marriage turns out to have been arranged due to interplanetary politics, casting doubt on whether or not he actually ever loved her.
- What the Hell Is That Accent?: As a native of Titan, the showrunners probably wanted Imra to have a peculiar voice that sounds nothing like any accent on Earth. People aren't that good at using accents they haven't heard, but thankfully Amy Jackson is from the small British nation of the Isle of Man, and has a very distinctive Manx accent that is unfamiliar to most of the world, and just sounds like someone from the Welsh valleys trying to do an American accent to Brits who aren't familiar with it. The strangeness may also be influenced by Jackson also living in Liverpool growing up, and then spending most of her adult life in Mumbai.
Reep Daggle / Chameleon
Known Aliases: Chameleon
Portrayed By: ???
A member of the Legion of Super-Heroes. According to Imra, he the first who was stricken by the Blight and 6 other legionnaires followed.
Nura Nal / Dream Girl
Species: Human-Naltorian Ancestry
A member of the Legion of Super-Heroes and descendant of Nia Nal / Dreamer.
- Alliterative Name: Nura Nal. Doubles as Alliterative Family given that her Famous Ancestor Nia also has/had them.
- Dreaming of Things to Come: This is her powers in the comic books which her Famous Ancestor uses in the show.
- The Ghost: Only mentioned by Brainy.
- Legacy Character: Her Dream Girl monicker is derived from her Famous Ancestor Nia Nal's codename, Dreamer.
- Mixed Ancestry: She has yet to appear, but her Famous Ancestor is/was a Human-Naltorian Hybrid.
Winslow "Winn" Schott Jr.
Portrayed By: Jeremy Jordan
Voiced By: Ricardo Bautista (Latin-American Spanish dub), Chikahiro Kobayashi (Japanese dub)
Appearances: Supergirl | Crisis on Earth-X note
Originally a CatCo computer programmer with a crush on Kara, he leaves the company to join the DEO starting Season 2.
- Adaptation Dye-Job: The Toyman's son is an Evil Redhead in the comics. Here he is brunet (and not evil).
- Adaptation Name Change: The Toyman's son in the comics is named Anton.
- Adaptational Heroism: The Toyman's son in the comics was the Post-Crisis-pre-New 52 incarnation of the supervillain Dollmaker. It was initially thought that Winn was this to the Toyman himself, but it's since been confirmed that Toyman is his father.
- Adorkable: He's very nerdy and openly enthusiastic about all things super and tech-related.
- Amazon Chaser: So far, two of the women Winn has been attracted to (Kara and Lyra) have been superhumanly strong and quite capable of kicking his ass without any problems. Furthermore, when Lyra breaks the padlock while breaking into the museum, he just get more excited.
- All Love Is Unrequited: Had a crush on Kara until late Season One.
- Ambiguously Bi: Openly had a crush on Kara and had a relationship with Siobhan and later Lyra, but repeatedly compliments Superman on his physical appearance. Jeremy Jordan has admitted to playing the character in this light.
- Betty and Veronica: He's the Adorkable Nerd (Betty) to James's Tall, Dark, and Handsome Hunk (Veronica).
- Boldly Coming: In "Mr. and Mrs. Mxyzptlk", he starts a relationship with Lyra, who hails from Starhaven.
- Brainy Brunette: He's a very good hacker and he has brown hair.
- Butt-Monkey: He tends to get picked on a lot — especially by the likes of Alex and Maggie.
- Camp Straight: He has the high, somewhat fluty voice often associated with gay men and was the one to design Kara's costume, also prone to flighty mannerisms, but is very into Kara.
- Commuting on a Bus: His actor leaves as a series regular after Supergirl Season 3 and will be reduced as a Recurring Character.
- Crouching Moron, Hidden Badass: Remember how Winn got his job at the D.E.O.: he out-hacked members of the professionally trained hackers of a secret, paramilitary organization specializing in alien technology. Not only that, but he designed anti-K armor for Superman and Supergirl.
- Dark and Troubled Past: He describes his father as a very bad man who very much deserves the prison cell he is stuck in. As of "Childish Things" that description is strikingly on point.
- Dogged Nice Guy: To Kara in Season One, bordering at times on Stalker with a Crush. He gets over it eventually, after his encounter with his father shows him the danger of bottling up his feelings.
- Expy: He borrows his Gadgeteer Genius and Nerd side from Cisco Ramon and the Hollywood Hacking of Felicity Smoak. After analyzing the portal bracelet Cisco gave to Kara, Winn admires Cisco's work so much he admits that if he ever gets a chance to meet him, he's certain the two would take an instant liking to one another. He's not entirely wrong in the assumption.
- Extraverted Nerd: A geek and not shy about it.
- Gadgeteer Genius: He designed Supergirl's suit, and later creates an anti-K suit for her and Superman.
- Hollywood Hacking: Kara's main tech genius. He can even hack into Brainiac's race and destroy them from the inside out.
- Hollywood Nerd: An all around geek, but even Cat calls him out as being "impishly handsome."
- Horrible Judge of Character: He has shown interest in a villain (Siobhan), a con artist (Lyra), and a girl who has only ever seen him as a friend (Kara). The man really needs better taste in women. However, Lyra eventually proved herself to be a better person, so it's at least somewhat subverted.
- In the Blood: Winn lives with the legitimate terror of this trope taking effect, given that he is the son of a psychopathic murderer.
- The Knights Who Say "Squee!": Only had elements of this in Season One. As a member of the D.E.O., he goes into full giddy mode over Superman.
- Masculine Girl, Feminine Boy: He's a Non-Action Guy, while all his love interests are capable of kicking ass.
- Mission Control: Starting in Season Two. He fills the role for both the DEO and Guardian.
- Nerd: Described as a "Comic-Con stalwart" in casting calls.
- Nice Guy: He's a friendly and cheerful guy by default, not to mention a shameless fanboy for superheroes, and always happy to help Kara. He really hits his stride after getting over his crush on her and joining the D.E.O., where he gets to live his dream.
- Not His Sled: Basically an inverse of how Superman: The Animated Series handled the Toyman, with Winslow, Sr. being the one who's Toyman.
- Not So Different: As much as Winn doesn't want it to be true, he realizes he does have one thing in common with his father: being afraid to reveal their true feelings.
- Odd Friendship:
- He bonds with Lena over tech in "Crossfire," and helps her save the day. They later work together very well in "Nevertheless, She Persisted."
- Quickly becomes Mon-El's closest friend, aside from Kara, and his other mentor in Earth customs and pop culture.
- Playful Hacker: He sure enjoys putting his technological expertise to good use and practically jumps at the chance to help the DEO.
- Put on a Bus: Leaves for the future in the Season 3 finale, as Brainy asks for his assistance against his evil relative Brainiac.
- Secret Keeper: Knows that Kara is Supergirl. He also finds out that Clark Kent is Superman.
- Shipper on Deck: He quickly notes the chemistry between Kara and Barry, though it's mostly because he likes seeing James denying his jealousy.
- Speaks in Shout-Outs: As the resident geek, he's the most likely to make science fiction and fantasy references while doing his job.
- Stepford Smiler: Despite the witty humor, he occasionally worries that he will end up like his father.
- Token Human: Became the only human member of the Legion in the Supergirl Season 3 finale.
- Voice with an Internet Connection: Acts as this alongside James for Supergirl when she isn't working with the DEO.
- Serves as a more explicit form of this for James as Guardian.
Querl Dox / Brainiac 5 / "Brainy" / Agent Dox
Known Aliases: "Brainy", Barney, Agent Dox
Portrayed By: Jesse Rath
Appearances: Supergirl | Elseworlds note
An alien from the planet Colu, hailing from the 31st century. He is a descendant of the Brainiac clan, and a member of the Legion of Super-Heroes.
After the end of Supergirl Season 3, he is forced to stay in the present due to the original Brainiac releasing an AI-killing virus in the future. He quickly joins the D.E.O.
- Abusive Parents: He implies his mother, at least, was rather horrible.Nia: Looks like your mother raised you right.
Brainy: Oh, no. She definitely did not.
- Adorkable: Incredibly socially awkward, but also a huge fanboy towards Kara and trying his best to relate to normal people.
- Affectionate Nickname: His friends call him "Brainy" (which is his canon nickname in the comics as well).
- Amazon Chaser: He's clearly smitten with Kara, even before they meet for the first time. However, he later falls for Nia.
- Awesome by Analysis: When confronted by members of the Children of Liberty, Brainy warns them that he will be forced to "use physics" to deal with them. True to his word, he wipes the floor with his assailants with strategic dodges and judo-like moves that results in them being knocked out by each others' attacks.
- Badass Bookworm: He primarily serves as support to other heroes, but proves more than capable of handling himself in a fight when necessary.
- Brutal Honesty: Has absolutely no sense of tact when he tells Kara that she is in a coma.
- Character Tic: He often holds his hands in front of himself with his fingers touching, generally as a thoughtful pose.
- Cyborg: He mentions that he's "techno-organic," and is capable of both high-speed calculations and emotions.
- Facial Markings: The glowing Brainiac symbol on his forehead.
- Fish out of Temporal Water: The primitive level of technology on 21st Century Earth horrifies him, and he ends up butting heads with Winn over the DEO's lack of "basic" things like Cold Fusion.
- A Form You Are Comfortable With: He has a device so he could appear human.
- Insufferable Genius: Not as much as his comic book counterpart, but is still prone to bluntly stating things and bragging about his superior intellect. By the end of his second episode, Winn proves to him that sometimes overthinking stuff doesn't help immediate matters.
- The Knights Who Say "Squee!": Even despite the dire straits, he can't keep down his excitement that Supergirl is actually talking to him.
- Legacy Character: He is a descendant of one of Superman's greatest foes, and relation of Season One villain Indigo, aka Brainiac 8.
- Manly Tears: Much to Lena's shock, he does show some actual emotions over Kara being forced into a protective armor due to the atmosphere being poisoned.
- The Medic: He operates the ship's medical bay, attending to Kara during her coma and treating Alex's injuries.
- Movie Superheroes Wear Black: His suit is black and very dark blue rather than deep purple.
- No Social Skills: Try as he might, Brainy's social skills are a sight to behold, at times. A small degree of it is due to being from a distant future with somewhat different social interactions, but he has dropped a few hints that he had similar issues even then.
- Promoted to Opening Titles: He becomes a main cast member in the fourth season.
- Relationship Upgrade: After a Anguished Declaration of Love, he and Nia eventually become a couple during the Supergirl Season 4 finale.
- Robot Girl: Gender Inverted. He casually mentions having an AI system, and is from the same clan as Robot Girl Indigo.
- Science Hero: He is primarily this for the others in the Legion, providing the strategy and tech support for them in battle.
- Ship Tease: Kara's love interest from the comics, and he spends the majority of his premiere episode bonding with Kara and squeeing over getting to meet her. Later however, he becomes Nia's Love Interest.
- The Smart Guy: The genius of the Legion, piloting their ship and treating injuries as needed.
- Superpowered Evil Side: Due to having Genetic Memory, he stores a part of the original Brainiac's consciousness inside of him, which takes over during the penultimate and final episode of Supergirl Season 4. This personality of him is much more ruthless and cunning.
- Technopath: His systems are capable of interfacing with the ship's technology.
- Trapped in the Past: Brainy is forced to stay in the past because the original Brainiac released a virus that is killing all AIs in the future.
- White Sheep: A heroic member of the Brainiac clan, unlike Indigo or his titular ancestor.
- 0's and 1's: He writes the binary code for a smiley face on Alex's cast.