A LongRunningBookSeries, beginning in 1927, for kids and teens created by the legendary StratemeyerSyndicate under the [[PenName pseudonym]] Franklin W. Dixon. They follow the adventures of Frank and Joe Hardy, a [[SiblingTeam pair of brother detectives]]. Frank is the logical, calm one, and Joe is the more impulsive, instinctual one. The series (alongside their DistaffCounterpart and frequent Crossover partner Literature/NancyDrew) invented or popularized most of the KidDetective tropes.

Originally created by the StratemeyerSyndicate, a prolific group of ghostwriters under the direction of Edward Stratemeyer (and his daughters, who took over when Edward died in 1930) that put out many successful children's books. Canadian writer Leslie [=McFarlane=] was the original writer of the first 16 books, writing them only to pay his bills and feed his family (getting ~$100 US for each book, with no royalties, which wasn't all that bad at the time; a large number of the original Stratemeyer ghostwriters were journalists, and using journalist salaries as comparison, $100 per book was roughly six weeks' salary for four weeks' work), and dreaded having to write the books (referring to the books in his diary as "the damn juveniles"), and by the mid-30s other writers began to write the books as well (such as John Button, whose books are infamous for their use of sci-fi elements, inconsistencies, and strange plots), leaving [=McFarlane=] free to forget about the books and write his own stories.

In the late 1950s until the early '70s, the first 38 books were revised and rewritten to update the stories (terms like "chum", "roadster", etc.), remove politically incorrect terms and stereotypes ("Negro", "swarthy foreigner", "Chinaman", "colored", etc.), as well as shortening the books from 25 chapters to 20 chapters. Newer books were also made, with the "original" series coming to an end in 1979 with #58. The original editions can be recognized by having dust jackets and plain brown (and later, tan "tweed") covers; the revised versions, beginning in 1961, have the cover picture printed directly on the book to better withstand being used and abused by kids.

After the books were acqired by Simon & Schuster (which took control of Grosset & Dunlap in the 70s after a lawsuit), the series was continued as "Digests". Later on, the DarkerAndEdgier ''Casefiles'' series was added and ran concurrently with the Digests. Both series have since been discontinued, the ''Casefiles'' in 1998 and the Digests in 2005. The series has since continued under the ''Undercover Brothers'' subtitle, which reinvents the brothers as agents working for an all-teen secret agency; there is also a corresponding graphic novel series.

The Hardy Boys have also appeared on TV many times:

* [[MickeyMouseClub The Mystery of The Applegate Treasure & The Mystery of the Ghost Farm]], two serials running on the original ''MickeyMouseClub'' in 1956 & 1957.
* TheHardyBoysNancyDrewMysteries on Creator/{{ABC}} in TheSeventies, which they shared with Nancy Drew, starring Shaun Cassidy & Parker Stevenson. Arguably the most famous of the TV incarnations.
* TheHardyBoysCasefiles, produced by {{Nelvana}} in the TheNineties, starring Colin Grey and Paul Popowich.
* WesternAnimation/TheHardyBoys, a 1969-1971 SaturdayMorningCartoon series that featured the Hardys as working undercover in their own rock band, with accompanying bubblegum pop albums and a group of live actors touring. It was notable for being the first cartoon to have an African American character.
* ''The Mystery of the Chinese Junk'', a 1967 Creator/{{CBS}} pilot that starred Tim Matheson & Rick Gates.

Definitely ''not'' to be confused with [[Wrestling/MattHardy the]] [[Wrestling/JeffHardy wrestlers]] of the same name.

They seem a bit prone to a CrossOver with Literature/NancyDrew.
!!This series provides examples of:
* AerithAndBob: Much like Literature/NancyDrew, there have been a few names that have fallen out of favor since 1927, and now come across like this. Just look at their close circle: Frank, Joe, Tony, Phil, Jerry, and Callie are quite common, Chet and Biff are marginal (and nicknames for Chester and Allan, anyway), but Iola just completely sticks out. Considering she was replaced with a girl named "Vanessa" in the ''Casefiles,'' it's possible the publishers thought so, too.
* AloofAlly: in the Casefiles series, the Gray Man and, by extension, the Network he works for.
* AnimatedAdaptation: CBS had a cartoon version which ran 34 episodes from 1969-1971.
* BigEater: Chet Morton, but both Hardy Boys seem to qualify as well. Joe sometimes rivals Chet's, and Frank, well...
-->'''Callie''': ''We polished off a huge pie at Mr. Pizza's. And I only had two slices.''
* BornDetective
* BrainsAndBrawn: respectively, Frank and Joe themselves are often compared to each other like this.
* TheCaseOf: The series used this a few times, with titles like ''The Case of the Counterfeit Criminals'' and ''The Case of the Psychic's Vision''.
* ChekhovsHobby: Chet Morton and his loads of hobbies that seems to change for each book.
** Frank and Joe are both guilty of this too.
* CityOfAdventure: A lot of stuff seems to happen in good ol' Bayport. Also averted, since the brothers travel all over the world when they stumble into mysteries.
** In the Hardy Boys, it's slightly justified. Bayport was a port city (duh), so some smuggling was expected. It makes less sense in Nancy Drew's hometown River Heights (although both were suburbs of cities which were known for mafia activity, New York and Chicago.)
* ChooseYourOwnAdventure: The "Be a Detective" series, which ran for six books and was a CrossOver with Nancy Drew.
* ClassyCatBurglar: Charity in the Casefiles. Fiona Fox in the '88 Super Mysteries.
* ClearMyName: the first three volumes of the ''Casefiles'' series all charges the Hardy with murder, but that was just part of the villains' plot.
* CliffHanger: One almost every chapter.
* CoolBike: In the most recent series of books
* CoolBoat: the ''Sleuth'' in the original series. Who knew that a term for a detective would be a good name for a boat?
** Their friend Tony's boat, the ''Napoli'', also qualifies, as it's used to help them out on a number of occasions.
* CoolCar: Several of them
** Subverted in the original books, where their car was described by Chet as looking "like a million dollars but drove like thirty cents", and can barely make 15 miles an hour.
* CrossOver: With ''Literature/NancyDrew'' in the "Super Mystery" series and ''Literature/TomSwift'' in the "Ultra Thriller" books.
* DarkerAndEdgier: The newer Hardy Boy ''Casefiles'' series. Iola Morton, Joe's long-running girlfriend in the original series, is blown up by terrorists about a second or two before the opening scene of ''the first book''.
** Not to mention that some cases would place tension between the brothers, which would often lead into not-so-friendly brawls between them. Later, it also modifies their relationship with the police (which is scarcely a problem in the original series), with an AscendedExtra of sorts in Con Riley as the only officer that takes their skills seriously. And then there are the Assassins, the terrorist group responsible for Iola's aforementioned murder, and are also the most frequently recurring villains in the series who, well...[[ExactlyWhatItSaysOnTheTin do exactly what you might expect]].
** The original edition of "The Sinister Signpost" features a vaguely middle-European villain named Vilnoff who [[spoiler: tries to destroy Bayport, and kills himself via electrocution to avoid arrest]].
* DistressedDude: Both of them, also Fenton and Chet on occasion.
* DivergentCharacterEvolution: As the years went on, Frank became much more bookish, logical, and occasionally downright shy around girls, while Joe became much more extroverted, temperamental, and a much bigger flirt.
* {{Doppelganger}}: In a Casefiles book, body doubles of the boys are made once they're captured. They play SpotTheImposter. [[spoiler:It turns out Iola kept a diary, so when Joe asks her questions, in standard trope fashion, "only she would know the answer to"...]]
* EagleEyeDetection
* EvenEvilHasStandards: when the BigBad of "Mystery of the Desert Giants" is captured, he plans on selling out his gang ''and'' framing an innocent man to feign his own innocence. His chief mook is so disgusted that he testifies to make sure the BigBad goes to jail, and mentions how he should never have been involved in the criminal racket in the first place.
* FatBestFriend: Chet Morton is the best friend of The Hardy Boys, and has been described as fat, plump, chubby, stout, heavy-set, etc. He has a huge appetite, and vacillates between types A, B and C as the plot dictates.
* FoodPorn: The series originally included extended, lavish descriptions of meals. Stratemeyer reasoned that since teenage boys have huge appetites, they'd appreciate such detail. Later editions of the earlier volumes saw such passages removed, in accordance with the growing preference of young readers for dialogue and action over description.
* FriendOrFoe
* GirlOfTheWeek: Happens pretty often in the ''Casefiles'' series, although they usually tended to go for Joe; the ones who would have eyes for Frank would have to be let down gently in the end because he's with Callie, of course.
** Goes in the opposite direction in the ''Undercover Brothers'' series. Frank, who is painfully shy around women and is easily flustered, seems to have every girl he sees fall for him, while Joe, who claims to be a smooth womanizer, can barely get the time of day. He has no clue how Frank does it.
* GuileHero: Especially at the Casefiles books when they are almost always have to fend for themselves to outwit their enemies. Frank in particular can be a very efficient [[TheChessmaster chessmaster]], but even Joe can pull a few tricks of his own.
* HardHead
* HaveAGayOldTime: Done intentionally by the most prolific of the authors, as a way of injecting humor into a job he didn't care for much. See more details [[http://www.10zenmonkeys.com/2007/10/29/how-gay-were-the-hardy-boys/ here]].
** ''WesternAnimation/SouthPark'' picked up on it.
--> ''I'm getting a '''raging''' clue right now.''
* HeroSecretService: the reason the Hardy Boys got involved with the Network in the first place: the Assassins are targeting Fenton Hardy through his family, and he calls on a small favor from the Network (who he had dealings with before) to keep his loved ones safe.
* HeterosexualLifePartners: Brothers though they may be, Frank and Joe also have this relationship in ALL of their different incarnations. Though their personalities change in the various series, one thing that is constant throughout is that they're a team and are inseparable, doing just about everything together and basically able to read each other's minds. They have their friends, and they have their girlfriends/love interests, but each of them is always the other's number-one priority.
** In the original series, they also had this relationship with Chet, who was involved in almost all of their adventures.
* KidDetective[=/=]AmateurSleuth
* KeepCirculatingTheTapes: Although Applewood Books reprinted the original versions of books 1-16 complete with the original bindings and dustjackets, the only way to get books 17-38 in their unabridged form is to hunt down original copies at thrift stores and eBay. Also, Applewood has stopped printing the books, but they can still be bought new online.
* LiveActionAdaptation: ''The Mickey Mouse Club'' adaptation in the 1950s; [[Series/HardyBoysNancyDrewMysteries ''The Hardy Boys Nancy Drew Mysteries'']], which ran from 1977-1979, and the short-lived ''The Hardy Boys'' in 1995.
** There have been rumors for a long time about "The Hardy Men," a live-action movie starring Ben Stiller and Tom Cruise as the Hardy Brothers as adults.
* LongRunningBookSeries
* MadeOfIron: Joe, who takes most of the punishment due to him being the "athletic" one.
* TheMeddlingKidsAreUseless: Former TropeNamer, due to the fact that in the early books, the Hardy brothers would often find out who did what, but at the same time the police were doing the same. Essentially, the had grand adventures but didn't affect much in the long run. This was later changed.
* NotAllowedToGrowUp: Joe is 17, Frank is 18. However, they're growing up slowly. In the 1920s, 30s, and 40s, Joe was 15 and Frank 16, in the 50s through 70s blue hardbacks, Joe was 16 and Frank was 17. Still, that's nearly a century for 2 years.
* NotNowKiddo: The Hardys met with this in a lot of the early books. Eventually, Chief Collig and Con Riley figured out they should probably listen to them once in a while...
* OddCouple
* PutOnABus: The majority of the Hardy's circle of friends have slowly faded away as time has gone by. Chet is still a regular, Biff Hooper and Tony Prito make rare appearances, but Phil Cohen and Jerry Gilroy seem to have completely disappeared.
* RecycledINSPACE: The 1969 animated show featured the Hardy Boys...as a hip groovy ''rock band''!
* ScoobyDooHoax: prominent in the original Hardcover series, where the titles give it away (''The Phantom Freighter'', ''The Ghost of Skeleton Rock''), although some are more subtle about it (for example, ''Secret Warning'' deals with both the ghost of a pirate ''and'' an ancient curse revolving around a golden Pharaoh's head). Even the ''Casefiles'' managed to squeeze in a seemingly supernatural plot at least once (''Cliff-hanger'' sees a mountaineering expedition on Yeti's Tower being threatened by the creature from which the mountain got its name).
* SiblingTeam
* SpinOff: There have been several:
** ''The Hardy Boys Casefiles:'' DarkerAndEdgier and HotterAndSexier series designed to appeal to teen audiences by removing the previous roadblocks of the parent series (NoHuggingNoKissing, NeverSayDie, etc.) Although it played up the violence and played down the romance compared to its DistaffCounterpart ''The Nancy Drew Files.'' Might qualify as a QuietlyPerformingSisterShow since it had a successful run of 12 years (1986-1998) and 127 issues.
** ''The Hardy Boys are: The Clues Brothers'' and ''The Hardy Boys Secret Files:'' SpinOffBabies series which both involve 8 and 9-year-old versions of Frank and Joe solving mysteries in the vein of missing pet cats.
** ''Hardy Boys: Undercover Brothers:'' Considered a continuation of the original series by the publisher, it hovers somewhere between the Originals and the Casefiles in terms of storytelling (less graphic than the Casefiles, but also more liberal than the Originals.)
** Both the ''Casefiles'' and ''Undercover Brothers'' spin-off had their own spin-off, a Crossover series with Nancy Drew. Interestingly, they were both titled ''Nancy Drew-Hardy Boys Supermysteries.'' (Fans tag them '88 and '07 for the sake of avoiding confusion.) Both shared a lot of similar traits, including hinting at Nancy/Frank and Bess/Joe relationships.
** ''The Hardy Boys Adventures:'' Set to begin in early 2013, this series will take the place of ''The Hardy Boys: Undercover Brothers'' as the "official" canon (meaning it's not considered a spinoff like the ''Casefiles'') and it appears it will try to fix some of the more disliked parts of ''Undercover Brothers'' (such as the first-person narrative and using actual paintings for covers instead of clipart.)
* SuddenSequelDeathSyndrome: [[spoiler: Iola]] in the first chapter of the first ''Casefiles'' book.
* TapOnTheHead: Frank & Joe have both been knocked out by getting hit in the head so often that, in real life, the two should be vegetables in permanent coma in the hospital.
* TeenGenius: Frank
* WHAMEpisode: the very first Casefiles book, with the death of Iola in the opening chapter.
* [[WhereTheHellIsSpringfield Where The Hell Is Bayport?]]: The most you really get is that it's a coastal town in New England within driving distance of New York City. The earliest series implies New York state, where there's an actual Bayport in real life, however, later materials will say New Jersey and Massachusetts as well.
* WorkingTheSameCase: Frank and Joe's investigations often end up coinciding with one their father is working on.
** Every. Single. Supermystery. No matter how different the two cases seemed to be, they would have their case tied together to Nancy's roughly two-thirds of the way through the book.