Kanto is where it all started for young Ash Ketchum in Pokémon. It was the first region of the series, and it has the original 151. The original Indigo League series sparks nostalgia and emotion for many an elder Pokémon fanatic to this day, and most can remember every Pokémon that Ash had on his roster during this era.
Ash caught many Pokémon during this time, and many of them rose to stardom while others left before accomplishing much for Ash. We are going to rank the Kanto Pokémon caught by Ash Ketchum here today, from the least useful on the roster to the absolute icons of his team.
20 Raticate
This one was briefly held by Ash during his ride on the good ship St. Anne. Ash traded his Butterfree for the Raticate but immediately felt buyer's remorse. Thankfully, Ash's trading partner allowed Ash to return the Raticate for his Butterfree.
19 Primeape
This one was another brief partner to Ash. He first caught Primeape as a Mankey when it stole his hat. Ash kept Mankey as it evolved into Primeape, but it never followed Ash's commands and went on frequent rampages.
Ash eventually earned Primeape's respect when he saved it from a great fall, but Ash decided Primeape was better off with another trainer that could better work with the Fighting-type Pokémon.
18 Haunter
After losing a battle to the Psychic-type Gym Leader, Sabrina, Ash decided that he needed a Ghost-type Pokémon to gain the type advantage over Sabrina's Pokémon. He met Haunter at the Lavender Town Pokémon Tower, and it agreed to help Ash battle against Sabrina.
Haunter never really followed Ash's commands either and mostly entertained itself by tormenting Sabrina's Pokémon. However, Ash was still able to win the battle, and he left Haunter with Sabrina as the two formed a friendship during the battle.
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16 Aipom
Ash met Aipom on his return trip to Kanto when he challenged the Battle Frontier. Ironically, it's a Johto-native Pokemon that Ash met after he finished his Hoenn journey, and it became more significant when Ash went onto Sinnoh.
In any case, this Aipom first became part of Ash's journey when it stole Ash's hat, and it followed Ash and his friends to the Grand Festival. There, it stole Ash's hat again, and Ash finally caught the Aipom. Aipom battled for Ash a few times, but Aipom proved more theatrical and well-suited for Pokémon Contests. Ash traded it to Dawn in the Sinnoh region for her Buizel. Aipom later evolved into Ambipom while in Dawn's care.
15 Riolu
Ash very recently received Riolu as an egg, receiving it from Nurse Joy. He had trouble hatching the Pokémon, and it ran away upon hatching. Ash retrieved it, and, though it hasn't had time to prove itself yet, Riolu shows a lot of promise as a partner for Ash.
14 Gengar
Ash caught Gengar recently after it was abandoned by its former trainer to haunt Professor Cerise's lab. It's a new addition to Ash's team, but it's already proven itself powerful and took down a Raichu at the World Coronation Series.
13 (30) Tauros
Ash caught 30 Tauros during his adventure in the Safari Zone. He sent them all to Professor Oak's Lab, but he has called upon one particular Tauros to battle at his side. Beyond that, the Tauros are known for stampeding across the fields surround Oak's Lab.
12 Muk
Ash met his Muk at the Kanto Power Plant. This Pokémon was also sent to Oak's Lab, where it got a reputation for being an affectionate Pokémon. However, Muk has battled on Ash's behalf a few times in the Indigo League and beyond.
11 Mr. Mime
Mr. Mime, or Mimey, was originally the partner to Ash's Mom, but it joined Ash on his journey through Alola and has stuck with him into Pokémon Journeys. Ash entered Mr. Mime into a Frontier Battle, where it held its own against a Hariyama, but then lost to a Mightyena.
10 Dragonite
Dragonite is another recent addition from Pokémon Journeys. It started off as a Dragonair that Ash taught how to fly and evolved into Dragonite while battling Team Rocket. It's already been through some tough battles, even beating a Mega Evolved Lucario at the World Coronation Series.
9 Kingler
Kingler is a particularly steadfast ally to Ash. He caught it as a Krabby, and it quickly evolved after that. Kingler stuck with Ash in Kanto and Johto, and it's proven itself to be a powerful Water-type Pokémon.
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7 Butterfree
Caterpie was the first Pokémon Ash ever caught, and he evolved it through its Metapod form into a Butterfree. It was one of Ash's most loyal companions for a long time and proved its prowess in many battles.
Butterfree eventually met a mate, and Ash let Butterfree go to start a life together with its newfound love.
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5 Squirtle
Ash's Squirtle first came to be a part of Ash's team after he encountered the Squirtle Squad, a gang of Squirtles that caused trouble for Officer Jenny and the nearby townsfolk. After joining up with Ash, Squirtle became a regular part of Ash's lineup. He eventually returned Squirtle to the Squirtle Squad, but can be called upon by Ash at any time.
4 Bulbasaur
Bulbasaur was an early catch for Ash, and it was the first of the Kanto starter Pokémon he caught. It was one of Ash's most accomplished and powerful Pokémon and opted to stay in its base form rather than evolve and change. It stuck with Ash for a very long time and only was sent to Professor Oak's lab to help keep the peace between Ash's many Pokémon.
3 Pidgeot
Pidgeotto was Ash's second Pokémon and became a loyal and powerful partner to Ash as well. Eventually, Pidgeotto evolved into Pidgeot to protect its fellow Pidgeotto and Pidgey's against attacking Fearow and Spearow in Viridian Forest.
Ash decided to let Pidgeot stay in Viridian Forest after this instance, as the Pokémon clearly wanted to be the guardian of its kin there.
2 Charizard
Caught as a Charmander, Charizard has been one of Ash's most mercurial teammates. It often acted out while it was a Charmeleon and evolved into Charizard to protect Ash from a rampaging Aerodactyl.
Charizard often disobeyed Ash after that, but it still proved to be one of his most powerful Pokémon in battle against Blaine and his Magmar in Kanto and Noland and his Articuno in the Battle Frontier. It spent some time in the Charific Valley to train and gain discipline, and it returned to Ash's team when he went to Unova.
1 Pikachu
Obviously, Pikachu is the top spot. It was Ash's first Pokémon, is the mascot of the franchise, and has stuck with Ash through every region since the first. It has shown endless personality and has battled against Gym Leaders, Elite Four members, and Legendary Pokémon.
Pikachu has fought everything and everywhere, though his battle against Lt. Surge's Raichu will always be one of his most memorable showdowns. Pikachu is obviously still Ash's best Pokémon.