The title of longest running anime is a surprisingly difficult question to answer, if only because there have been so very many anime that have hundreds of episodes that it's not immediately obvious. As long-running favorites such as One Piece and Case Closed (also known as Detective Conan) sail past the thousand-episode mark, viewers marvel at the staying power of anime. These are series that have been on the air for longer than some of their viewers have been alive, racking up episode counts into the hundreds or even thousands, to the point where it would take weeks to marathon just one of them.

Whether these series and franchises are some of the most famous of all time, such as One Piece, or obscure but still fresh like Crayon Shin-chan, they all have something that has kept audiences coming back to them for decades. Other anime come and go, but these series have stood the test of time.

20 Dr. Slump Arale-chan - 243 episodes, 5 Years Airing

Dr. Slump was a manga created by Dragon Ball legend Akira Toriyama, and was his biggest work prior. The series follows Arale Norimaki, a little robot girl, as well as her creator Senbei Norimaki, as they deal with the other strange residents of Penguin Village. Dr. Slump has actually crossed over with Dragon Ball a few times, with Goku appearing in Dr. Slump's 1997 remake and Arale appearing in Dragon Ball and Dragon Ball Super. The series ran from 1981-1986, so it didn't have much overlap with Dragon Ball when it came to airing. The series is mostly a low-brow comedy, much like early Dragon Ball, and would likely be appealing to fans who enjoyed the original Dragon Ball.

19 Hamtaro - 296 episodes, 6 Years Airing

Hamtaro is a children's show about the eponymous hamster, Hamtaro, and the friends he makes as he lives his life as a pet. Unusual for an anime, it's based on a children's book series rather than a manga. Hamtaro's anime debuted in 2000 and ran until 2006, following 296 episodes starring Hamtaro and his Ham-Ham friends. Hamtaro is probably best known in the West from its run on Cartoon Network around that time, although it was aimed at a bit of a younger demographic than many of its fellow programs. Hamtaro was popular enough to also produce four movies and a number of video games, and Hamtaro lives on as a segment of the Japanese children's show Norisuta Hai!

18 Fairy Tail - 328 episodes, 10 Years Airing

Based on a manga created by Hiro Mashima, Fairy Tail is a long-running action/fantasy anime that focuses on Natsu Dragneel, a Dragon Slayer wizard who works for a guild known as Fairy Tail, who meets and teams up with a woman named Lucy Heartfilia. The Fairy Tail anime debuted in 2009 to wild success and went on to run until 2019, for a whopping 328 episodes total. The manga's follow-up, 100 Years Quest, is said to be receiving an adaptation soon as well, so this huge number of episodes will only get bigger before long.

17 Sgt. Frog - 358 Episodes, 7 Years Airing

Sgt. Frog, also known by its original title Keroro Gunso, was based on a manga by Mine Yoshizaki. The story follows a platoon of five frog-like aliens who are attempting to conquer Earth, but constantly fail due to their incompetent and lazy leader, the eponymous Sergeant Frog. While the manga was aimed at teens, the anime has a much younger demographic. Episodes are usually split into two roughly 15-minute segments, akin to many Western cartoons. The series ran from 2004 to 2011, airing an episode a week for that entire time period, making it impressively consistent, if nothing else.

16 Bleach - 366 Episodes, 8 Years Airing

Bleach is an anime following the adventures of Ichigo Kurosaki, a newly reborn Soul Reaper who dedicates his life to defending the defenseless and easing the torment of lost souls. With his newfound powers, the fate of the world is in Ichigo's hands as he battles evil and saves innocent lives. Bleach began its long run in 2004, going on to air for the next eight years before coming to an epic conclusion in 2012. By the time the anime came to an end, it had aired 366 episodes, becoming one of the longest-running anime series of all time. The show's legacy still lives on to this day through its brand-new sequel series, Bleach: Thousand-Year Blood War, which has aired an additional 26 episodes and counting.

15 Gintama - 367 Episodes, 12 Years Airing

Former swordsman Gintoki Sakata has left his life of bloodshed behind and now gets by doing odd jobs around Japan alongside straight-man samurai Shinpachi, outrageously powerful alien girl Kagura, and Kagura's giant dog Sadaharu. Together, they are the Yorozuya Gin. Gintama is set in a world where aliens were the primary cultural influence over Edo Period Japan, meaning that any ridiculous thing that could happen, will happen. These include a character turning into a gorilla after being bitten by one, a four-way swordfight over toilet paper, and one of the best beach episodes in anime, rounding out a 367-episode run over twelve years.

14 Kochikame: Tokyo Beat Cops - 373 Episodes, 8 Years Aired

Kochikame: Tokyo Beat Cops is a comedic anime series following the exploits of Kankichi Ryotsu, a middle-aged cop in Tokyo, and his other friends on the police force and in the city. The series is based on a well-loved serial, which ran for several decades before the animated series ever hit television. Korchikame: Tokyo Beat Cops has a tremendous backlog of episodes for new and old fans alike, with eight years of content to sift through. Ultimately, the series came to an end in 2004 with 373 episodes in total but has continued to produce new content in the form of nine television specials, the most recent of which aired in 2016.

13 Dragon Ball - 639 Episodes, 32 Years Airing

An absolute cornerstone in shounen anime, Dragon Ball is based on the long-running manga by Akira Toriyama, which in turn is based on the Chinese novel Journey to the West. It follows the life of Son Goku, one of the only survivors of the alien warrior race called Saiyans, from childhood to adulthood. Through the three series that directly adapt the manga and the anime-only Dragon Ball GT, Goku not only becomes stronger but gains friends and family as well. He fights through several tournaments and apocalyptic threats to the Earth. Since death is rarely permanent in this universe, stories often feature recurring Dragon Ball characters fans think should have stayed dead.

12 Naruto - 720 Episodes, 15 Years Airing

Even without counting the sequel series Boruto: Naruto Next Generations, which currently has 293 episodes, Naruto is one of the longest-running series of all time, with its second part, Naruto Shippuden, making up the bulk of its runtime. Naruto Uzumaki starts off as a lonely orphan with untapped potential and ends up majestically coming into his own as a great hero. Of course, some could say that Naruto cheats a little in this category: much of the episode count is built up by filler episodes. While Naruto: Shippuden's filler is often maligned, some arcs have produced some of Naruto's best villains.

11 Shima Shima Tora No Shimajiro - 726 Episodes, 15 Years Aired

Shima Shima Tora no Shimajiro is a must-see series for fans of the slice-of-life anime genre. The long-running anime series is directed at younger children, aiming to teach them important lessons about beginning school, making friends, listening to parents, and more. The series began its historic run in 1993, running for over 700 episodes over the span of fifteen years before coming to an end in 2008. This was, however, only the original series that came to an end, with successor series adding to the show's legacy, with a cumulative total of well over 1,000 episodes.

10 One Piece - 1,075 Episodes, 24 years airing

An all-time favorite worldwide, One Piece is based on one of the longest-running manga ever. It is a faithful adaptation with very little filler. Just before his execution, the world's most notorious pirate, Gol D. Roger, declared that he has hidden his ultimate treasure, the One Piece. Whoever completes the impossible quest and finds the treasure will become the new Pirate King. As Eiichiro Oda's manga is still ongoing with no signs of stopping yet, it may well overtake some currently longer anime in the near future. Time will only tell how far Luffy and the Straw Hats' story will have stretched when it finally ends.

9 Case Closed - 1,067 Episodes, 26 Years Airing

Shinichi Kudo is a brilliant young detective, already assisting seasoned police on big cases with his lightning-fast analyses. However, with success comes enemies: two criminals attack Shinichi and force-feed him experimental poison. Instead of killing him, the poison turns him into a child, forcing him to adopt a new identity as he continues to try and solve crimes. It's a testament to the strength of the show's writing that viewers are still tuning into Shinichi's latest cases even as they number over one thousand. While a running thread is Shinichi's attempts to return to his old body, Case Closed is largely episodic.

8 Gundam - 1,118 Episodes, 44 Years Airing

Gundam is one of the most famous and prolific anime franchises of all time. Even without counting specials and OVAs, the canon TV series keep coming and coming. They tell the stories of brave pilots commanding powerful flying mecha called Gundams, in order to win wars and protect loved ones across dozens of alternate universes and timelines. Some of the most famous Gundam series are the original 1979 Mobile Suit Gundam, Zeta Gundam, and Mobile Suit Gundam Wing. The most recent, Witch From Mercury also earned critical acclaim upon release. Though the quality of each series varies, Gundam has a better track record than many other classic anime series.

7 Crayon Shin-chan - 1,122 Episodes, 30 Years Airing

A slice-of-life anime with some of the most ridiculous character designs in anime, Crayon Shin-chan follows five-year-old Shinnosuke Nohara. A typical troublemaking kid, Shin causes untold amounts of mischief around his hometown with his friends. The series is still airing in Japan, and multiple attempts have been made to dub it in English, though each is mostly incomplete. All the English dubs take considerable liberties with the source material, such as the Vitello Productions dub adding in even more dirty jokes to an already lewd show.

6 Yu-Gi-Oh! - 1,177 Episodes, 25 Years Airing

Who says card games shouldn't be taken seriously? Yu-Gi-Oh! is a massive franchise that began in 1998, and hit the international stage big-time in the early 2000s. The original Yu-Gi-Oh! series ran for 224 episodes, but like Gundam, it rapidly grew into a monstrous franchise, made up of 11 different series at this point with more on the way. Like Pokémon, it has a well-established real-life card game that constantly manufactures new content to base new series on, meaning that so long as the card game remains popular, new Yu-Gi-Oh! anime series are likely to keep on coming.

5 Pokémon - 1,257 episodes, 26 Years Airing

So long as Pokémon games keep getting made, new seasons of the anime will keep on coming. The young Trainer Ash Ketchum and his partner Pikachu travel through region after region, catching new Pokémon, making new friends, and winning battle after battle in hopes of becoming a Pokémon Master. The show continues to be a hit worldwide among audiences of all ages, with Pikachu being a favorite in many countries. While its stakes aren't exactly high, it's bright, optimistic, and more than fun enough to keep viewers coming back for more. Ash's run in the anime ended after 1,232 episodes and 25 years, but a new future for the series has already begun with Pokémon Horizons.

4 Chibi Maruko-Chan - 1,359 Episodes, 27 Years Airing

Chibi Maruko-chan is a must-watch single-season anime, but it may be harder to marathon than the average 12- or 24-episode season. With an episode count well into the thousands, it would take over three weeks to finish the whole thing. An adaptation of one of the most famous shoujo manga, the children's show follows Momoko "Maruko" Sakura and her family and friends. It is lighthearted and cute, and is good for both older viewers who are feeling nostalgic and younger viewers who want something simple.

3 Soreike! Anpanman - 1,572 Episodes, 34 Years Airing

Sorieke! Anpanman follows the adventures of the bean-headed eponymous children's superhero Anpanman as he battles evil, including the nefarious germ Baikinman. The series is a cultural staple of Japan, with Anpanman becoming one of the most recognizable original characters from Japanese pop culture. Due to the main character's prominence in Japanese popular culture, Sorieke! Anpanman has enjoyed a lengthy run as a television series. Beginning its tenure in 1988, the series is still continuing to this very day, with over three decades' worth of storytelling and over 1,500 episodes.

2 Doraemon - 1,787 Episodes, 26 Years Airing

Doraemon has long been a staple of the anime medium, with several series bearing the name running for long stretches of time. The 1979 series in particular, however, has managed to garner the longest tenure of the franchise. The 1979 rendition of Doraemon ran for twenty-six years and aired over 1,700 episodes before coming to an end in 2005. Though the series is still far from the longest-running anime's episode count, the total amount of episodes in the entire Doraemon pantheon is over 3,000.

1 Sazae-San - 7,920 Episodes, 53 Years Airing

Sazae-san doesn't just outstrip every anime in history in terms of library and longevity, but it is one of the longest-running TV shows of all time, soundly beating heavy hitters like The Simpsons and Doctor Who. It even holds the Guinness World Record for the longest-running television animated show ever. The show chronicles the daily lives of housewife Sazae Fuguta and her family, and it is beloved in Japan for its portrayal of a wholesome Japanese lifestyle, with many families still tuning in every Sunday night. It is such a cultural staple that "Sazae-san syndrome" is the recognized term in Japan for depression caused by the end of the weekend and the impending start of a new workweek.

While many of these anime have very little presence even in the dedicated Western anime fandom, their longevity is still incredibly impressive, considering how many are shows aimed at very young children, a notoriously fickle demographic. The rest, on the other hand, are staples of the medium in Western fandoms, to the point where it'd be nearly impossible to find an anime fan who hasn't watched at least one episode of Dragon Ball or One Piece. These series have maintained their longevity due to the quality of their overall storytelling, even in spite of ups and downs over the years. While some of the longest running anime series may be unexpected titles, all that really means is that fans may have some new long-lasting favorites to try out.