The title of longest-running anime is a surprisingly difficult question to answer, if only because there are so many anime that have continuously aired episodes for decades. 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.

Whether these series and franchises are some of the most famous of all time, such as One Piece, or more obscure to Western fans, 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 Gintama (2006-2010), Aired for 4 Years

Produced by Sunrise, based on the manga by Hideaki Sorachi

Coming in at 201 episodes is Gintama, which follows the unusual samurai Gintoki Sakata as he travels, performing odd jobs and selling services in an alternate history version of Edo-period Japan, where aliens known as Amanto have begun an invasion. He's ed on his adventures by Shinpachi, whose sister he saved and who decided to become his apprentice, and an alien girl named Kagura, who possesses super-strength.

The series is primarily a comedy, heavy on gags, and even breaking the fourth wall on occasion. With laughs, solid action, a surreal setting, and an oddly compelling plot, Gintama proved it deserved its longevity.

19 Yo-kai Watch (2014-2018), Aired for 4 Years

Produced by OLM, Inc. based on the Video Games by Level 5

With 214 episodes in its original series, Yo-Kai Watch is based on the video games of the same name, and follows Nate Adams, who accidentally frees a Yo-Kai, Whisper, from a capsule machine. In gratitude, Whisper gives Nate a Yo-Kai Watch, a device that will allow him to summon various Yo-Kai, provided he has befriended them and received a medal from them. Accompanied by the cat Yo-Kai known as Jibanyan, Nate meets other Yo-Kai, both friendly and not, and uses their powers both in battle and to help people.

Yo-Kai Watch is undoubtedly for kids, and seems constructed to have been a rival to Pokémon. While it never reached those heights, it's had a fair degree of success, with numerous spin-off series and a number of video games released.

18 Yu-Gi-Oh! Duel Monsters (2000-2004), Aired for 4 Years

Produced by Studio Gallop, based on the manga series written by Kazuki Takahashi

With 224 episodes, the original Yu-Gi-Oh! makes for an interesting entry in the longest-running anime competition. The story follows Yugi Muto, a young boy in possession of a mysterious ancient puzzle which he assembles, causing him to develop another persona, commonly known as "Yami Yugi." Yugi is a top-tier player of the card game Duel Monsters, and after defeating his greatest rival, is approached by a villain who stole his grandfather's soul using another ancient artifact. Yugi is forced to enter a high-stakes tournament in order to defeat this foe and win his grandfather's soul back.

Full of absurd action sequences and some occasionally baffling card games, Yu-Gi-Oh! was a major hit in the early 2000s, and sparked a massive franchise full of follow-up series that are also quite long runners, such as Yu-Gi-Oh! 5D's and Yu-Gi-Oh! Arc-V.

17 Dr. Slump Arale-Chan (1981-1986) Aired for 5 years

Produced by Toei Animation, based on the original series by Akira Toriyama

At 243 episodes, Dr. Slump Arale-Chan is yet another series by Akira Toriyama, based on his manga that he worked on before Dragon Ball. It follows the android child Arale, created by an inventor named Senbei Norimaki, who aimed to make the perfect little girl robot. A comedy, Arale gets up to all manner of hijinks as she explores Penguin Village and the world beyond, and the series even has a crossover with Dragon Ball at one point, with Goku visiting Penguin Village during the original anime.

A gag series full of puerile humor and puns, Dr. Slump Arale-Chan is a comedy that's sure to cause just about any viewer to crack a smile, and because of its gag-based nature, there's very little continuity to worry about.

16 Dragon Ball Z (1989 - 1996) Aired for 7 Years

Produced by Toei Animation, based on the original series by Akira Toriyama

Surprisingly short compared to other long-running series – and its reputation – Dragon Ball Z sits at 291 episodes after running for seven years, and is one of the most recognizable entries of the shonen franchise. Dragon Ball Z picks up five years after the conclusion of the original Dragon Ball, opening with the Saiyan Saga, an iconic arc in shonen anime history that reintroduced Dragon Ball fans to Son Goku and his son, Gohan.

While it would be easy to lump all the Dragon Ball franchise's anime adaptations together to celebrate just how long the anime has been ongoing, it's also important to just how different each of these entries are, and how the distinctions between them shape the greater narrative in Dragon Ball's lengthy and beloved history.

15 Fairy Tail (2009-2019), Aired for 10 Years

Produced by A-1 Pictures, Dentsu Inc., Satelight, Bridge, and CloverWorks, based on the Manga by Hiro Mashima

Coming in at 328 episodes is Fairy Tail. Fairy Tail follows the story of Natsu Dragneel, a dragon-slaying member of a wizarding guild known as Fairy Tail, as he explores the land in search of a dragon, Igneel, who is actually his long-lost father. Natsu is ed on his quest by the likes of young wizard Lucy Heartfilia, the cat-like Happy, and eventually, the ice wizard Gray Fullbuster, mage knight Erza Scarlet, and Wendy Marvell, a fellow dragon slayer.

The series is known for its wacky action and whimsical setting, but also for having substantial fight scenes and dramatic moments. With a sequel, Fairy Tail: 100 Years Quest currently running, the franchise only stands to get longer.

14 Sgt. Frog (2004 - 2014) Aired for 10 Years

Produced by Studio Sunrise, based on the original manga by Mine Yoshizaki

Boasting nearly 400 episodes over its entire run, Sgt. Frog is an anime that, while more niche to western audiences, is adorably iconic back in Japan. The series follows a small troupe of frog-like aliens occupying the planet Earth from their home planet, Keron. While the adorably unassuming aliens want to eventually conquer Earth, each of their attempts ends in failure, instead leading to slapstick hijinks involving the human characters.

Filled with adorable puns about frogs (ex., Planet Keron being named after the Japanese word for a frog's ribbit, kero), and a generally wholesome sense of humor, it's easy to forget just how many episodes there actually are in the anime.

13 Bleach (2004 - 2012), Bleach: Thousand Year Blood War (2022 - Present) 15 Years Airing

Produced by Studio Pierrot, based on the original manga by Tite Kubo

Despite not quite measuring up to the other of the "Big 3" shonen series of its time in of episode count, Bleach still maintains a spot as one of the longest-running anime of all time, especially considering how the series has made a huge comeback in the way of the ongoing Thousand Year Blood War, adapting the series' final arc.

Following Ichigo and the other of the Soul Society, Bleach is iconic for not only being one of the first anime to find mainstream success with western anime fans, but also by influencing new age shonen mangaka like Jujutsu Kaisen's Gege Akutami.

12 Naruto (2002 - 2017), Aired For 15 Years

Produced by Studio Pierrot, based on the original manga by Masashi Kishimoto

One of the original shonen 'Big 3", Naruto has had a lasting impact on the anime and manga industries, inspiring modern talent and influencing the direction of modern Shonen Jump titles. The series follows the titular Naruto Uzumaki, a young boy shunned by the people in his home village. Despite aspiring to someday become the Hokage of the Hidden Leaf Village, he faces a constant uphill battle learning that his body is the host of the Nine-Tailed Beast, and setting himself on a quest to bring back his friend and rival Sasuke Uchiha that shapes the main, driving plot of the story for decades.

With over 720 episodes between Naruto and the anime's sequel, Naruto: Shippuden, the anime has solidified itself as being one of the most iconic anime ever produced, even if much of its episode count is padded out by non-canon filler content.

11 One Piece (1999 - Present), 24 Years Airing

Animated By Toei Animation & Based on the Manga By Eiichiro Oda

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. One Piece's anime began in 1999 and has since produced 1,090 episodes at the time of writing. Time will only tell how far Luffy and the Straw Hats' story will have stretched when it finally ends.