Kid Hero



He'll fight off hordes of monsters with techniques the likes of which master swordsmen would never equal. He'll wield weapons spoken of only in the oldest of legends. He'll save the world and everyone in it from destruction five times over.

And he'll do all of this while not even being old enough to drive.

The Kid Hero is, as the name implies, a child. The exact age varies up and down the scale, from 8 to 17, but they're never an adult by whatever the local standards are. The "base age" seems to be 14 or thereabouts, though their numeric age may not be revealed.

Your standard Kid Hero has a strong streak of immaturity in them. They might well regard the adventure as a game, albeit one with slightly higher stakes. (Often their starting weapon is explicitly made of wood.) Expect this to be scrubbed out of them in short order, usually when the place they call home gets wiped off the map.

Kid Heroes DO have some things going for them, though: their idealism and youth. A villain trying to perform a Hannibal Lecture on a Kid Hero is in for a rude awakening when he gets it thrown back in his face. Kid Heroes, quite simply, have a very clear view of right or wrong. Some may call it naive, but it serves them well, as they are basically impossible to corrupt. They're also at that age where their self-image is intricately intertwined with their friends, so they often kick ass through the Power of Friendship.

A Kid Hero will commonly, but not universally, have two primary adversaries; his most dangerous opponent is usually an adult villain who serves as the hero's Arch Nemesis, while his second most dangerous opponent will usually be a younger villain, closer to his own age or slightly older, who serves as the hero's Evil Counterpart. These two are rarely affiliated, but if they do work togther, the adult will almost certainly be the Big Bad with the young villain as an extremely reluctant and rebellious Dragon.

Most commonly seen in console and computer role-playing games, as it allows for character growth to feel natural and skips the question of why they aren't properly equipped for the job. Also appears in the vast majority of animated action-adventure, both Western and Eastern.

If a television show is specifically focused on this character, then the description will most likely be along the lines of "Saving the world, and doing homework!"

If particularly well executed, The Brigadier and others won't look like monsters or weaklings for sending a kid to do their heroics for them.

This is Older Than Feudalism; examples include the Biblical hero David, and several Greek and Hindu mythic heroes (e.g., Hercules, who killed two large snakes sent by Hera to kill him in his crib)

See also Child Soldiers, a much more realistic (and darker) concept. Compare Kid Samurai. Contrast Enfant Terrible, a common antagonist of such a character.

Anime and Manga

 * Basically Shonen anime and manga in general. That and magical girls.
 * Kouji Kabuto from Mazinger Z was sixteen when began the series. His Battle Couple, Action Girl Sayaka Yumi and their friend Boss were the same age, and his brother Shiro was roughly ten-years-old. Tetsuya Tsurugi and Jun Hono from Great Mazinger were slightly older (although you would be hard-pressed to tell with Tetsuya, since he might be quite inmature sometimes). It is hard to tell if Duke Fleed from UFO Robo Grendizer was underage or not, but Hikaru Makiba and his sister Maria were still teenagers.
 * Ryoma, Hayato, Musashi, Benkei and Michiru from Getter Robo were high-school students when the sereis began.
 * Hiroshi Shiba from Kotetsu Jeeg was also underage. And an amateur car racer. And Cyborg capable transforming into the head of an Humongous Mecha. And he looked after his mother and little sister after
 * Akira Hibiki from Raideen was a high-school student.
 * Hyoma Aoi and his Five-Man Band from Combattler V were all teenagers.
 * Kenichi Go and his Five-Man Band -two of which were his brothers- from Voltes V were also underage.
 * Kazuya Ryuuzaki from Daimos also seemed a teenager... even though he was an astronaut.
 * Horribly and brutally deconstructed with Zambot 3. The three main characters are pre-teenagers were pushed by their families to pilot a Humongous Mecha and fight a genocydal psychopath intended to wipe all humans off Earth. At the same time they were hated by the people they were intending protecting. Needless to say, they were through serious breakdowns, emotional abuse and got a final mind-screw. This series went to extreme lengths to show children should not be used like soldiers, depicting infant abuse in a way unparalleled until then.
 * On the other hand, Daitarn 3, a Lighter and Softer Spiritual Sequel to Zambot 3, played it straight. Banjo Haran was a Hot-Blooded, sixteen-years-old James Bond spy with a Humongous Mecha lived on a manor and was surrounded by beautiful women.
 * Tetsunosuke in Peacemaker Kurogane.
 * Mahou Sensei Negima: Nagi Springfield during his youth certainly qualifies. At age 10, he wins the Mahora Tournament, and could fly without a staff and essentially teleport. Gathering a team of badasses and becoming a war hero, he receives the title of Thousand Master at age fifteen. His son and series protagonist, 10-year-old Negi aims to be just like him - he's already led his side to victory in the Battle of Mahora "game", and was able to go toe-to-toe with one of his father's contemporaries in an all-out fight.
 * Summed up in one line from Bleach; when Chad is offered the chance to end the battle and drink with Shunsui Kyōraku, he refuses. When asked why, he points out, "It's illegal for minors to drink;" it's quite easy to mistake Chad for an adult..
 * Along with Chad, Ichigo, Orihime, and Ishida are all 15. (17 now.) Rukia is about 150 years old, and shorter than mostly everyone.
 * In the Galaxy Angel games, the player character is 21 and only one Angel is over 18. Galaxy Angel II has a 16-year-old player character and Angels from ages 11 to 21 (not counting Nano-Nano, who, as a Robot Girl of sorts, is probably about two).
 * Deconstructed in Neon Genesis Evangelion. 14-year old Shinji has a complete breakdown under the pressure of being the designated hero, whereas Asuka suffers a similar breakdown and Rei suicides all over the place.
 * One of the episodes is even titled "And he was aware he was just a child".
 * Shinji and Warhammer 40 K un-Deconstructs the trope in spectacular fashion. That Shinji's mercenary force of Assault Terminators are recruited mostly from what used to be Macedonia does not go unnoticed by Admiral Yang.
 * Simon from Tengen Toppa Gurren Lagann, like Shinji, starts out as a cowardly boy; however, since his mentor is Kamina the Determinator, instead of Gendou the cold-hearted, borderline Magnificent Bastard, Simon later becomes a Badass Kid Hero.
 * Goku is a Kid Hero for most of Dragon Ball. Child Goku was so popular in Japan, that they tried to bring him back for Dragon Ball GT by having him wished into a child with the Dragon Balls.
 * In Dragonball Z, the Kid Hero role was filled by Gohan, and after the Cell saga, Trunks and Goten.
 * One of the main characters of GaoGaiGar, Mamoru Amami, is a rather interesting example of a normal boy who develops into a Kid Hero over the course of a series. Originally an ordinary grade school student, Mamoru becomes the Tagalong Kid to the heroes of the Gutsy Geoid Guard because he's the only one who can purify Zonder cores and turn them back into humans. Apart from flight and a rather potent shield which he can't consciously manifest (at first), he has no combat ability whatsoever, and his first attempt at purifying a Zonder on his own nearly gets him killed. At some point, however, the sheer awesomeness of his coworkers began to rub off on the little guy, and by the end of the tv series he'd racked up a few Crowning Moments of Awesome despite still not having any real combat ability, and goes up against Humongous Mecha-sized opponents on more than one occasion without getting squished. Then FINAL rolls around, and Mamoru comes back after an extended absence on Earth with several shiny new Levels In Badass; his healing powers have developed into a full-blown Holy Hand Grenade, his shield is capable of tanking direct hits from mecha-scale energy weapons, and he gets a Final Battle with his very own Evil Counterpart. And just to put the cherry on the kid's Awesome Cake, Mamoru's courage and refusal to surrender single-handedly tips the scales of the Final Battle by powering up the G-Stones of all of 3G's giant robots, giving them the energy for a chain of My Name Is Inigo Montoya moments. Not bad at all for an eight-year old.
 * The planned though sadly cancelled crossover between Betterman and GaoGaiGar would have had him finally promoted to piloting a mecha along with Kaidou.
 * In Naruto, the main characters start around 12, in part II they're 15 and more recently Naruto's age is revealed to be 16.
 * 15-year-old Garrod Ran, an ex Street Urchin, becomes the pilot of the titular Gundam X Real Robot, with his also 15-year-old love interest Tiffa Addil following him in his adventures. His Team Dad and mentor as well as Tiffa's adoptive father, Jamil Neate, used to be a Kid Hero as well... but he actually had a complete breakdown after the war, which didn't let him pilot a mecha in more than 15 years.
 * This holds true for most Gundam series. The only ones who are never underage are Kou Uraki, Domon Kasshu, and Shiro Amada.
 * The Pokémon universe guarantees this since all Pokémon trainers start when they turn 10.
 * It should be noted that while that only applies to the anime, most trainers in the manga are around ten - eleven when they start.
 * This is true. You're allowed to become a trainer at age 10. You don't have to become a trainer then, it is possible to become a trainer later.
 * Luffy from One Piece barely counts at age 17, but many people look at him as younger. Most of the early members of the crew are rather young, too. Word of God wants to reinforce that minors still shouldn't drink.
 * Practically every main protagonist in a Magical Girl series falls under this. As of this writing, probably the only ones that are of adult age are the 26-year-old Agnes Bell from My Wife Is A Magical Girl and the 19-year-old Nanoha Takamachi from Magical Girl Lyrical Nanoha StrikerS.
 * Nanoha and her original friends are all in their mid twenties now. However, they still command a lot of teen heroes.
 * The student meisters and Weapons in Soul Eater are mostly around the age of 13, which is either stated or can be deduced from various comments and flashbacks. Those who are noticeably older are the Thompsons (Liz, at least) and Tsubaki. Thunder and Fire are by far the youngest Weapons, or at least it appeared so until the latest chapter (briefly) 'aged' them via a power-up. There may have been some sort of timeskip following the Baba Yaga arc, but the art evolution and absence of a clear timeline make it difficult to tell.
 * In the Monster Rancher Anime, Genki is said to be around ten or eleven (The clearest indication comes from something a dragon says). It goes without saying that Genki is a complete and utter badass. His very first fight starts with him kicking a genetically modified velociraptor in the face. And not a little kick either, hell no. He is portrayed as being chosen-one who can do things nobody else can, however.
 * Jin in Zettai Muteki Raijin-Oh; pretty much every main character in the Eldoran series apply.
 * Jintetsu of Steel in Kurogane.
 * The titular character from Hayate the Combat Butler.
 * Yuri Shibuya from Kyo Kara Maoh.
 * Edward and Alphonse Elric from Fullmetal Alchemist. Edward joined the military at the age of 12, and during the events of the manga, he's 15 (turns 16 at some point). Alphonse is one year younger.
 * Tsuna Sawada from Katekyo Hitman Reborn
 * Haru Glory from Rave Master (no surprise who voices this character in the English dub)
 * Renton Thurston from Eureka Seven. Mind you that this character is voiced by Johnny Yong Bosch instead of Yuri Lowenthal in the English dub (he was originally though).
 * Joey Jones from Heroman, more appropriately, The Kid with the Remote Control.
 * Yusuke Urameshi from Yu Yu Hakusho, is 14 throughout most of the series. Kuwabara is around his same age.
 * Every protagonist of all Digimon series, both anime and manga, except Digimon Savers (and even it still has a few).
 * Kimba from Kimba the White Lion combines this trope with A Child Shall Lead Them.
 * The Bokurano kids thought they would become this. THEY WERE WRONG.

Comic Books
"Billy (after reverting back): My name's Billy Batson. But maybe it's too dangerous to be Billy anymore."
 * Stan Lee took a wild shot by making the Spider-Man the first second third true teen superhero (i.e. non-sidekick; there was the Star-Spangled kid back in WWII, but he didn't sell as well). The eventual widespread popularity of Spider-Man quite possibly is the root of the trope within the West.
 * The Ultimate Marvel version of Spidey remained in the 15-16 age for the duration (160 issues) of his run. His successory, Miles Morales, is only 13. Just to hit Miles' age home, Nick Fury holds his hand when showing him around the Triskelion. Neither Miles nor Fury seem to be bothered by it. Both Spider-Men are realistically proportioned, so there tends to be David Versus Goliath dynamic with many villains.
 * Years before, the prepubescent Billy Batson became Captain Marvel, and subsequently the most popular character in comic books. A lawsuit from DC eventually ended his reign, but the incident proved that children, like so many demographics, react best to people like themselves.
 * Of course, Captain Marvel has the twist that he becomes an adult in his super powered form.
 * One retelling of Captain Marvel's origin deconstructed this somewhat. Big Bad Doctor Sivana got some intel that Billy Batson (homeless and living in a subway tunnel at the time) was Captain Marvel and sent assassins after him. Billy defeated them, but his best friend was fatally shot in the process. Billy was so enraged that he nearly violated Thou Shalt Not Kill with regards to Sivana. When Superman confronted him about it, Billy decided to show him his true nature.

"Superman: He's a little boy. He should be worrying about homework and school and the crush he has on the girl sitting next to him in class! Not worrying about assassins killing his best friend! He's just a boy. This is a burden meant for men."
 * Needless to say, Superman was pissed and he called out Shazam for handing all of the responsibility and danger that comes with life as a superhero to a little boy.


 * Though Shazam had pointed out that Billy was the only person on Earth who could be entrusted with the power of the gods. So he countered Superman's statements with "He's a boy . . . who could use some guidance." Cue Superman revealing his Clark Kent identity to Billy and the two becoming true friends.
 * Also pre-dating Spidey by some years was Superboy ("the adventures of Superman when he was a boy"), who debuted in More Fun Comics #101 in 1945, and soon moved to a lengthy run as the lead feature in Adventure Comics, plus gaining his own self-titled series (Superboy) in 1949.
 * The Marvel Universe superteam Power Pack all got their powers before the age of thirteen, and one of them had already retired from adventuring (more than once) by the time she was seventeen.
 * Most of the cast of Runaways are teenage superheroes, though Molly Hayes probably epitomizes this trope best. She's 11 years old and has super-strength, plus invulnerability. However, like a young child, she tires easily and has to take naps when she's over-exerted. (In other words, she could probably go a round or two with the Hulk, but would probably fall asleep mid-battle.) Her idea for a superhero name? Princess Powerful (Hey, she's 11, give her a break!).
 * Garth from Ghostopolis looks to be around 10 or 11.
 * The Teen Titans, at least in their original run, was composed of the teenaged sidekicks of adult superheroes. Later versions of the Titans were mostly composed of college age superheroes, but still had members who were barely old enough to shave (like Beast Boy).
 * The Titans' successor Young Justice was also a group of Kid Heroes, even younger than the original Titans.
 * The Golden Age Star Spangled Kid and his modern age namesake are both teenage superheroes (with adult sidekicks). Courtney Whitmore, the modern Stargirl, still wears braces on her teeth.
 * Loki of The Mighty Thor is getting a run as this, having been reincarnated as a kid. He skips most of the negative tropes because he's got a focused mission (save Thor from the Serpent), it's pointed out that he's in a lot of danger (he's a god, but a gos in the body of a kid without his magic), and most of all, he's not acting like Scrappy Doo and charging into situations (at least physical situations) that he can't handle. He book is currently considered one of the best Marvel is putting out right now.
 * All the Robins!

Film (Animated)

 * Coraline, of course!
 * Pinocchio.
 * eMMM in We Are the Strange
 * Maruti/Hanuman from The Return of Hanuman is considered as this.

Film (Live Action)

 * Anakin Skywalker, who single-handedly (if accidentally) won the Battle of Naboo at the age of eight. (Some would also call Luke a Kid Hero as well, even though he was 19 at the time of A New Hope)
 * I doubt that Luke would do. That is about normal military age
 * What, we're not including Jacen, Jaina and their group of friends in the Young Jedi Knights series? Going further down the timeline, we have Ben Skywalker, though his hero's journey puts a lot more emphasis on spirituality rather than saving the galaxy.
 * More recently, it's been about getting his father to accept his Sith Apprentice girlfriend...
 * Spy Kids
 * The title character from Kirikou and The Sorceress is actually a BABY hero.
 * Harry Potter is a kid in the first two books/films. More like a teenager in the later ones, and an adult by the end.

Literature

 * Pretty much all of Diana Wynne Jones work directed towards a younger audience. (And sometimes they share the spotlight with adults.
 * The four Pevensies in The Chronicles of Narnia are schoolchildren when they save the land and become monarchs.
 * Peter Pan is a kid, though a very old one who never grew up.
 * Tamora Pierce's protagonists grow up with the books, but
 * Alanna, Kel, Sandry, Tris, Daja, and Briar are 10 at the beginnings of their stories
 * Daine is about 13.
 * Bekah and Aly are between 16 and 17.
 * Evvy is ten in her first appearance, but by the time she gets her own book, she's fourteen.
 * All installments of The Neverending Story.
 * Ender's Game - except becomes a partial subversion when.
 * Garion from David Eddings' Belgariad.
 * Harry Potter had his first adventure at the age of eleven and in the last book he defeated Lord Voldemort at seventeen. In additon to Harry himself, the series includes Ron Weasley, Hermione Granger, Neville Longbottom, Ginny Weasley, Luna Lovegood and the list goes on. On the other side, Draco Malfoy became an official Death Eater at sixteen.
 * Done somewhat differently in the Grey Griffins book series, in that while the main heroes are four children, adults frequently end up having to rescue them or help out, and are also the ones who do the overwhelming majority of the actual fighting. On the other hand, the kids tend to do much adventuring on their own, usually using their wits.
 * The Young Wizards series. Justified by several reasons:
 * The younger a wizard, the more raw power they have available.
 * A wizard is first offered his/her power by the Powers That Be when s/he is the best (or the only) solution to a particular problem, a problem which was directly or indirectly caused by the Lone Power, the Big Bad of the series. Thus, whatever a wizard does after first getting his/her powers is always important, and often dangerous.
 * In Sandy Mitchell's Ciaphas Cain novel Cain's Last Stand, the students at the schola. Starting with Sprie who is piloting Cain's shuttle when the attack comes and analyzes it for Cain. At one point, Cain observes that the schola could pass for an Imperial Guard post if the faces weren't so young.
 * Most of the Oz books have a child as at least one of the protagonists. Dorothy Gale is the most famous, but the books also include Tip, Princess Ozma (when she takes part in the action), Betsy Bobbin, Ojo the Unlucky, and others.
 * All the half-bloods and Grover in Percy Jackson and The Olympians. It's debatable whether or not the Hunters of Artemis count too - technically they are immortal and therefore mostly in their thousands, but physically are prepubescent.
 * Grover's thirty-two in the last book, he just looks sixteen.
 * Thalia of the Hunter of Artemis has to count, because she was fifteen when she became a Hunter in the third book.
 * Robb Stark from A Song of Ice and Fire. The guy commands a good percentage of the continent's armed men while barely old enough to grow a beard.
 * The series is full of those. Jon Snow and Dany are very notable.
 * Eragon in The Inheritance Cycle, though, in fairness, Eragon really isn't too far off from what his people consider the age of maturity when the series begins.
 * Gratuity in The True Meaning of Smekday, though she is a bit more mature at the start of the book than most Kid Heroes.
 * We All Fall Down by Robert Cormier has one of the few true subversions of this trope. The hero is introduced as an idealistic kid who calls himself "the Avenger" and daydreams of being a Vigilante Man, getting his chance after watching a break-in and rape.
 * Most of the protagonists of The Prophecy of the Stones are in their teens. The three main girls (four, counting Joa) are 14, Love Interest and leader of La Résistance Adrien is 16, and the Supporting Leader and Big Good  is 18.
 * Biggles is a borderline example, being eight months shy of his claimed seventeen years when he arrives as New Meat at the Air Training School in Biggles Learns To Fly. Most of the franchise is set some time after he reaches adulthood, however.
 * His sidekick Ginger is an odd example, appearing in one story as a Bratty Half-Pint before taking up an apprenticeship at an aircraft manufacturer to reappear a few books later, slightly Older and Wiser.
 * Most of Redwall's heroes are the Talking Animal equivalent of about twelve-to-fifteen.
 * Jack in The Talisman.
 * King is pretty fond of this trope: the kids in IT, Mark in 'Salem's Lot, Jake in The Dark Tower series, even Danny in The Shining.
 * Alcatraz Smedry of the Alcatraz Series.
 * The six main characters of the Animorphs series start out at the age of 13, with the exception of Ax (though he's still basically the Andalite equivalent of a teenager, since he's an aristh, or cadet).
 * Septimus Heap: Septimus and Jenna re both 10 year old by the first book.
 * In Warrior Cats, several of the heroes are apprentices when we first see their points of view - the feline equivalent of 10–18 years old - and some POVs start even younger.
 * Pretty much everyone in Someone Elses War, which is a book about Child Soldiers trying to rebel and escape from the Lord's Resistance Army.

Tabletop Games

 * In the Yu-Gi-Oh! (Tabletop Game), there's actually a monster called Hero Kid, which acts as an unofficial member of the Elemental Hero archetype.

Video Games

 * Overall it would probably be easier to list aversions to this trope in regards to Eastern RPGs. This trope is more a rule than an exception there, as underlined by the "Logan's Run Rule" of The Grand List of Console Role Playing Game Cliches.
 * Crono from Chrono Trigger and Serge from Chrono Cross. Both still living at home with their mommies (and said home surprisingly does not blow up.)
 * Sora from the Kingdom Hearts series; he starts puberty between the first and second games, apparently immediately after the first one, if you go by his voice in Re: Chain of Memories. Although naturally that has to do with the fact that Haley Joel Osment only recorded it after Kingdom Hearts II.
 * Ryu from Breath of Fire 3 and Breath of Fire 2's Ryu, who starts the game (along with Bow) as a young tyke literally equipped with a tree branch. His attacks even do a measly one damage to rub it in.
 * Most heroes—as well as most party members—of the Tales (series) are in their mid-teens. Tales of Symphonia features two party members who're 12 physically. Tales of the Abyss takes it to new extremes with a major character who's only 7. Tales of Vesperia stands out for having the party led by a 21 year old, the youngest human member is still 12 though (their is a 4 year old but he's a dog, so still an adult).
 * Most Final Fantasy games usually have heroes in their early to mid 20s, exceptions being the Onion Knights in Final Fantasy III (and their representative in Dissidia, Rydia (first third of the game), Porom and Palom in Final Fantasy IV, Relm and Gau in Final Fantasy VI, and Luso and Marche from the Final Fantasy Tactics Advance.
 * Several of the main characters from the Suikoden series of games.
 * Both Justin and Sue from Grandia - with a surprising dose of realism thrown in towards the end of the game, when Justin is forced to realize the seriousness of his quest, and
 * Any and every protagonist in Pokémon are between ten to eleven years old when they start, from the game's heroic mimes, to the anime's star Ash, to the many manga protagonists - about the only ones to be even in their late teens are Wes from Pokémon Colosseum and an obscure side game protagonist.
 * While the protagonists in Pokémon Black and White are older then eleven by a few years, they're still teenagers and thus count.
 * Mario & Luigi: Partners in Time seems to mock the concept by making Baby Mario and Baby Luigi two of the heroes who you control, along with their older counterparts, Time Travel and all. Of course it has to start with a Lampshade Hanging moment with Baby Mario rescuing Baby Peach by stomping Baby Bowser.
 * Tecmo's Secret of the Stars for the SNES had its action divided between a group of warrior children tasked with saving the world, the Aquatallion, and a group of adults, the Kustera, whose only purpose is to provide support for them.
 * Alex in Lunar.
 * Ratix in Star Ocean, Claude in Star Ocean the Second Story, Fayt in Star Ocean: Till the End of Time... notice a trend?
 * Dean in Wild ARMs 5 and Jude in Wild ARMs 4.
 * Perhaps taken to its extreme in Dragon Quest V, where the protagonist begins his heroic career at the age of five, and stores stock steel weapons and iron plate armor for children that age.
 * In Illusion of Gaia, Will (the hero) appears to be approximately 12–15 years old, with everyone in the game referring to him as a "child". The game story spans over half a year, and naturally he does grow up quite a lot by the end of the game... but he was already fairly mature to begin with, unlike most kiddie heroes.
 * Billy Hatcher and the Giant Egg All the main characters are young children not more than 10 years old apparently
 * The Zelda games, with Link usually being around 11 years old with the exception of Zelda II the Adventure of Link, The Legend of Zelda Ocarina of Time (via time travel), and The Legend of Zelda Twilight Princess where he's around 17. He may be a little older in The Legend of Zelda Skyward Sword.
 * In Fallout 2, it is possible to design a character as young as 16. This has no bearing on the rest of the game, though, and the character is still very capable of performing the things other characters can. These things include drinking, doing drugs, having sex for various reasons, having a shotgun wedding, and becoming a pornstar (or fluffer, if lacking in talent). Oh, and killing your way through the game by various, interesting means.
 * Every main character of all three MOTHER games, except Duster, Boney and possibly Teddy. Exemplified by main protagonists Ninten, Ness and Lucas.
 * The heroes in Golden Sun are another example. Isaac, Garet, Jenna and Mia are 17 years old and Ivan only 15. They're referred to as "children" by most of Weyard's populace.
 * In the sequel, however the party still features the under-age girls Jenna (still 17) and Sheba (14), the main hero is 18 years old and Piers
 * Kirby, from the eponymous series of games, is described as being a "little boy" (though his age is never directly given). In the anime, it's explicitly stated that Kirby is a baby.
 * The Sonic the Hedgehog series is full of this, with Sonic himself being 15 years old. In fact, some of his pals haven't even reached 13 yet, including Tails and Amy Rose.
 * Note that Tails is not only less than 13, he's 8, and one of the most competent heroes in the entire series.
 * Justified. They're animals. Hedgehogs, echidnas, and foxes don't live as long as humans do, so Sonic and Knuckles are actually adults. Tails probably still counts though.
 * The Kid in I Wanna Be the Guy.
 * Brian of Quest 64 is said to be 10 years old...or 5 years old according to the time period in which it took place.
 * The lords in the Fire Emblem saga are more often than not over 18, but some are young enough to be kid heroes:
 * Marth is 16 in Shadow Dragon.
 * On the same league, Celice from Geneology of the Holy War is 16 years old when he becomes the leader of La Résistance against The Empire. In addition, almost all of Celice's companions are around his age: his cousin Leaf (the hero in FE 5), his best friend Rana, etc..
 * Roy from Fire Emblem:. Sword of Seals is 15 years old an has to command his trope after his father, Eliwood, falls gravely sick and cannot do that himself. Some of his companions like The Archer Wolt and Sue, Fragile Speedster Thany, White Magician Girl Clarine, Child Mages Lugh and Ray, and Magic Knight Lilina, are around his same age.
 * Lyn's original age in the Japanese version of The Blazing Blade is 15. She was 17 going on 18 in the NA release, though. Eliwood and Hector are 17 in their own tales (16 in Lyn's tale, which took place a year earlier) as well. Wil is also 17, Serra and Priscilla are both 16, Rebecca and Erk are both 15, and Nino is 14.
 * Orta in Panzer Dragoon Orta is only an early- to mid-teenager. Iva Demilcol is even younger (not even ten) and he was recruited into the Imperial army.
 * Both Mega Man Battle Network and Mega Man Star Force follow this trope, with the main characters Lan and Geo being both fifth-graders (this also goes for their friends, especially in Battle Network's case).
 * Marco Van de Land from the fighting game Battle Fantasia is one of the main characters, fitting the trope to a T. Following in his father's footsteps and wielding an oversized zweihander, he has a habit of crying and whining, much to the annoyance of the rest of the cast. His brother Urs may also qualify as a Kid Hero, but with different quirks.
 * Kid genius Commander Keen, of The Nineties video games of the same name. He even saves his own babysitter in one game, and it's discovered that the Big Bad who keeps trying to blow up the galaxy is  Oddly enough, the developer of the (good) Keen games was id Software, who went on to produce significantly more mature games like Wolfenstein 3D, Doom, and Quake.
 * Kiddy Kong in Donkey Kong Country 3.
 * Applies to Diddy and Dixie as well.
 * Klonoa, the star of his game series, is stated to be twelve in Lunatea's Veil, therefore in its prequel he must be the same age or younger in Door to Phantomile—at least before it got remade, he looks older in the Wiimake of DtP. Though, since he's not human, the years might work differently for him.
 * Boy in A Boy and His Blob is that in both NES and Wii version.
 * Children of Mana has Ferrik, Poppen, and Tamber, with Poppen the youngest of them all, at nine years old.
 * Inazuma Eleven's casts are a group of junior-high soccer players who saves the world and soccer society from gods wannabe, aliens, and invaders from future... with soccer games.
 * Raz in Psychonauts is a prodigy at a summer camp for psychics. The adults have their competence either power dampened from the beginning, or Deus Exit Machina'd before anyone has a clue something is going wrong.
 * Lightning Legend Daigo no Daibouken has Daigo Raioh, a 14-years young martial artist, and descendant of a legendary Hero who defeated and sealed away the Demon King Dragless 450 years before the game's proper. Dragless being about to free himself, Daigo goes on a journey to defeat him for good.
 * The Persona series makes frequent use of this, since each game frequently has a high school as one of its major settings, and high schoolers (usually in their 1st and 2nd years) make up most of the playable cast. Ken Amada is the most obvious example, still being in grade school.
 * In the Madou Monogatari series, Arle starts her adventures while in kindergarten.

Web Comics

 * Lampshaded in this Scandinavia and The World strip
 * Tegan, the lead character of Holiday Wars, is a Kid Hero who's mission is to take out the Easter Bunny.
 * Played glaringly straight in FTales of the Questor; it is even Lampshaded in one strip when the Mayor said he wanted Quentyn to mature before sending him out.
 * Justified in City of Reality, as the titular city is sufficiently peaceful that they deliberately recruit kids to be members of SUEPR.
 * All sixteen protagonists of Homestuck are thirteen-year-olds or the alien equivalent. However, none of them act like it most of the time, some more so than others.

Web Original

 * The characters from Hyperion Academy, a Super-Hero School, range in age from 13 to 16. Likewise, the kids at the Venture Institute, another Super-Hero School.
 * Similarly, Nicholas Chandler, from Things That Go Bump In The Night is a 14 year old boy who is perhaps the most feared monster-hunter on Earth (he once killed a monster he thinks of as The Boogeyman with a baseball bat).
 * Ruby Rose from RWBY. She's the youngest and least mature of the entire cast, but is a combat prodigy and masterfully wields a weapon that is both unique and described (by someone who would know) as "one of the most dangerous weapons ever designed".

Western Animation

 * Ben 10 has a ten-year old protagonist named Ben Tennyson, who gains the power to turn into ten (or more) different aliens. However, he rarely acts more mature than usual for that age.
 * Although a bit more mature and determined in the sequel, Ben 10 Alien Force, 16-year-old Ben Tennyson still fits into this trope. Well, considering the English voice actor of this character who normally gets these kinds of roles in anime, video games, and western cartoons alike.
 * Ben is now a full-fledged Kid Hero in the Grand Finale Ben 10: Ultimate Alien.
 * Kim Possible
 * Subverted by the Grand Finale once she and her partner graduate from high school.
 * The Powerpuff Girls
 * Atomic Betty
 * Danny Phantom
 * My Life as a Teenage Robot
 * Aang on the Asian-influenced Avatar: The Last Airbender: that with tasks such as confronting a supreme monarch and restoring the political balance of the world, it seems almost cruel that such a burden should be placed upon a 12-year-old boy. To an end, this was essentially his initial reaction when presented with the entire concept, and most Avatars don't even start anything like this until they're 16. Fortunately, thanks to the series' focus on Character Development, he's moved forward a bit from being an irresponsible, self-centered, blissfully carefree, stereotypical 12-year-old kid who uses the word "fun" in every other sentence. He does however occasionally get depressed by how much he is responsible for being the Avatar. Can't blame him though, because after all, he didn't have much of a choice in the matter.
 * Additionally, the task of undoing the effects of the hundred-year-long war rests on the shoulders of sixteen-year-old Firelord Zuko. Good luck with that!
 * Actually, whole main cast are children saving villages and world from psycho villains.
 * The Teen Titans source material actually had the heroes as young adults overcoming the fact that they weren't kids anymore and continuing their heroic exploits regardless. However, since the cartoon series was being directed towards children, they were de-aged to around 15-17.
 * Dave, in the Veggie Tales episode "Dave and the Giant Pickle." After all, it is a retelling of the story of David and Goliath.
 * Blinky Bill
 * Zak Saturday of The Secret Saturdays.
 * The Fairly OddParents: Ten year old Timmy Turner, while he often fits the trope Designated Hero because he causes as many problems as he solves, there have been cases where danger has occured through no fault of his own, and he does step up to the plate and become a genuine hero. Wishology is the most known example of this.
 * While Teen Titans plays the trope straight, Batman Beyond: Return of the Joker horribly deconstructs it with  Being a kid doesn't/won't spare you from
 * ReBoot deconstructed it when Enzo took over Bob's role as guardian. He's nowhere near as good as Bob was and fails four episodes in, losing an eye in the process. One Time Skip later and Enzo is a cynical hair-trigger temper Anti-Hero who hates the kid he used to be.
 * Young Justice with Word of God promising a little deconstruction. For the sake of all Robin fans, hopefully nothing like Batman Beyond: Return of the Joker.
 * Wakfu has Evangyline (17), Tristepin/Sadlygrove (16), and Amalia (14). But the real standout is Yugo, who is about 10-ish but defies some aspects of this trope by being more cheerful and positive, as well as *gasp* capable of handling Teleport Spam responsibly instead of just being a Bratty Half-Pint.
 * You think one Kid Hero, or a small group of Kid Heroes is something? The Kids Next Door (from, where else? Codename: Kids Next Door) is a worldwide organization full of them!
 * The three main characters in Teamo Supremo fit this description.

Real Life

 * The Royal Navy permitted newly-minted midshipmen to go to sea and at least nominally command enlisted men from the age of twelve in the era of Wooden Ships and Iron Men, and it was not unheard of for men to reach lieutenant before their 18th year. The minimum peacetime recruitment age for enlisted men in all three services remains a relatively tender 16 years to this day.
 * Many, many underage boys lied about their age to serve in the First World War, rather fewer in the Second. Some ended up promoted or decorated for courage under fire, though for most things ended rather worse.
 * Audie Murphy, of To Hell and Back fame was a mere 14 years old when he enlisted and was about as close to some of the wilder fictional examples of this trope as you're probably going to get in Real Life.
 * Alexander the Great.
 * Budapest's Corvin Square has a memorial for several young boys who joined to protest against communist oppression, and were killed by the Soviets.
 * According to legend, Genghis Khan was 13 when he took control of his tribe and slowly built up his forces and conquered the most land mass of any military leader to date. Your Mileage May Vary if he was a hero or not though.