Ricky was a young boy, he had a heart of stone...—Skid Row, "18 and Life"
The formal adjective definition of the word "delinquent" describes something or someone who fails in their duty. This sums up its more popular usuage quite nicely; a delinquent is someone (generally a young person) who fails in their "duty to society" by being anti-social. They won't be plotting to take over the world or rob banks and they're more likely to be an Asshole Victim of The Aggressive Drug Dealer than an example. They are, however, likely to refuse to turn up to school (or are disruptive of they do), harass people in the street, shoplift and drink or smoke (possibly even both!).
If the protagonist encounters them, they're probably going to either be bullied by them, or fall in with them. In the later case they'll serve as Poisonous Friends who use peer pressure to encourage the protagonist to join them in their misdeeds (naturally this "friendship" will be short lived, as the protagonist will be caught the moment they try it and subsequantly be abandoned by them at best or made their Scapegoat at worst). Alternatively, the trope can be played more lightly, with a delinquant acting as a sort of Token Evil Teammate, or as an outright Anti-Hero.
Delinquents have come in many types in different times and places, but the stereotype tends to attach itself to whatever scary new subculture the kids have come up with recently: greasers in 50s America, mods and rockers in 60s Britain, punks everywhere since the 70s.
For tropes and stereotypes about delinquents in Japan, see Japanese Delinquents.
- Cromartie High School has an entire cast of delinquents (and a robot delinquent...and a gorilla...and Freddie Mercury), though they mostly spend their time talking about who they think is the toughest, rather than proving it by having a brawl.
- Kouji Kabuto from Mazinger Z skipped school and used rough language.
- England from Axis Powers Hetalia was said to be quite the delinquent as a teen, something which he fervently denies due to his current status as a (self-proclaimed) gentleman. This is also touched in Gakuen Hetalia where in England's official bio it mentions how he had been given such a reputation in the past.
- Harlem Beat: Kiriko, Kosuke, Sawamura love to smoke, gamble and skip school. And then there's the Kyan team.
- Airs Blue from Infinite Ryvius, a gang leader who gets his hands on the only gun on the Ryvius.
- Parodied in Minowa Hijiri from Bakuon!!, a Spoiled Sweet lonely rich girl who wants to be a delinquent, but doesn't seem to really understand what it takes to be one. She thinks that beating the other members of the motorcycling club at a game of Chicken -- while riding in the sidecar of a cycle driven by her butler -- qualifies her, and takes a rather innocent joy in thinking she's now a "bad girl".
- John Bender from The Breakfast Club, though he's actually a pretty nice guy when you get to know him.
- The vampire gang in The Lost Boys.
- The East Side Kids series from the 1930s & 40s, switching between the main characters and the supporting players.
- Cars featured a quartet of troublemaking young cars composing of a purple and gray car with rocket boosters as their leader, a green and white car with oversized spoilers, a blue van with speakers all over his body, and an orange drag racer with an oversized engine.
- Deconstructed with Rebel Without a Cause, in which the teens act the way they do because they lack competent guidance from adults. In fact, the main character of the film, Jim, wants to be a good person, except society - including his own parents - is keeping him form being so.
- Tom and Huck of Mark Twain's The Adventures of Tom Sawyer and The Adventures of Huckleberry Finn, making this one Older Than Radio.
- The main characters of the book The Outsiders are a typical greaser gang.
- Blackboard Jungle, a schoolteacher drama from The Fifties that helped codify this trope; the movie adaptation was the first major motion picture with a Rock N Roll soundtrack.
- Billy Nolan and his friends in Stephen King's Carrie. His girlfriend Chris is also one of these, though the film adaptations downplay it.
- iCarly: Sam has been arrested more than once, asks Freddie to hide her backpack when a cop shows up at Carly's apartment, was seen shaking down some kid in the pilot, solves most of her problems with violence, is generally the first (and only) member of the main threesome to suggest criminal action... you get the idea.
- Northern Exposure: Chris in the Morning was car thief and a con in his youth.
- Happy Days: Fonzie is a semi-reformed delinquent.
- That '70s Show: Hyde is a lifelong delinquent even after he becomes the manager of his own record store.
- The video for Aerosmith's "Livin' On The Edge" depicts several of these.
- Most of the characters in West Side Story.
- Basically everyone in Grease, even if they are singing the whole time.
- Jonny Warner of Zombie Prom is treated as a delinquent. He has a motorcycle, but the most rebellious thing he does is spell his name without the customary "h".
- "Three Juvenile Delinquents" from Noel Coward's Ace of Clubs.
- Alex of The Colour Tuesday, mostly due to no one taking her Synesthesia seriously as a kid, and authority figures generally putting her down even for reasonable things. In reality, she's less an actual delinquent and more the Only Sane Girl in a world where the adults are morons. As it turns out, having the adults be pawns of the Others doesn't help matters. Alex's status as a rebel is a sign of her destiny to break the control of the Others.
- The Mooks of the school level in No More Heroes.
- Riki and Kunio (Ryan and Alex) from the Kunio-kun (River City Ransom) series, including Super Dodgeball. Also about everyone else. Well, except the shop keepers, waiters, children, the old man at the sauna, Roxy, and Ryan. But still!
- Daigo Kazama, Eiji "Edge" Yamada and Gan Isurugi from Rival Schools. Of course, the school they attend is nothing but deliquents.
- In the sequel Project Justice, they're joined by female delinquent Aoi "Zaki" Himezaki and her all-female gang, the Ladies Team. The two gangs even face off against each other in the game's story mode, as illustrated above.
- Akira, from the near-future chapter of Live a Live, is the very image of a delinquent. He even slouches.
- Masamune Date and his men from Sengoku Basara. Think Sengoku Era biker gang.
- The Bloody Fists in Survival of the Fittest version two start out this way, but eventually turn into a full fledged criminal gang. Alexander Stevens, leader of the Hellbirds, also qualifies, though he tends to avoid making trouble in the schools themselves.