From Bulbapedia, the community-driven Pokémon encyclopedia.
Ash Ketchum (Japanese: サトシ Satoshi) is a Pokémon Trainer from Pallet Town whose goal is to become a Pokémon Master. He is the main protagonist of I Choose You! and M21, Pokémon movies set in a different continuity from the main series. Despite having largely the same personality as the Ash of the main series and starting out his journey in a similar way, the rest of Ash's story developed in quite a different way.
I Choose You!
Ash putting on his hat
for the first time
On the day Ash was supposed to pick up his first Pokémon and start his journey, he overslept and arrived too late at Professor Oak's Laboratory. Professor Oak informed him that the three starter Pokémon had already been taken by other Trainers from Pallet Town: Gary, Marina, and Tierno. There was, however, a fourth Pokémon, a stubborn Pikachu. Ash decided to choose Pikachu and, after receiving new clothes from his mother, he left Pallet Town and started his journey.
After scaring off a herd of angry Spearow, Ash and Pikachu started to bond when a Ho-Oh suddenly appeared in the sky. They looked in awe at the sight of this unknown Pokémon, as Ho-Oh dropped a Rainbow Wing. Ash picked it up and then saw a rainbow appear in the sky. Smiling, he promised Pikachu that they would both meet Ho-Oh again someday. Continuing his journey, Ash ventured inside Viridian Forest, where he eventually encountered a Caterpie. With the help of Pikachu, he managed to catch it. He also decided to qualify for the Pokémon League and managed to win three Badges.
Ash and Pikachu on their journey
Ash eventually met two other Trainers, Verity and Sorrel, while chasing after an Entei. After the Entei ran away and it started raining, they went looking for shelter. While doing so, they encountered a lonely Charmander on a rock, weakened from the pouring rain. After a brief argument with Charmander's original Trainer, Cross, Ash and Verity took Charmander to a cave. Sorrel healed Charmander and it fully recovered by the next day. Offering it a chance to join Ash on his journey, Charmander accepted and was caught by Ash. Ash continued his journey with Verity and Sorrel, and after he told them about his Rainbow Wing and desire to see Ho-Oh, the three Trainers decided to go to Raizen Mountains, where Ho-Oh was said to appear.
After encountering Cross again and losing a battle against him, Ash started to question himself and his Pokémon, especially after Cross called him the worst Trainer he had ever seen. Ash faulted his Pokémon for the loss and due to his change of heart and personality, the Rainbow Wing turned dark. Unbeknownst to him, Ash had been followed and watched by a Marshadow for some time. Marshadow decided help him bond with Pikachu again by pulling him into a dream that made Ash realize what his Pokémon meant to him and see the error in his ways.
Eventually, Ash, Verity, and Sorrel finally reached the Raizen Mountains and its highest peak Mt. Tensei. As Ash proceeded to place the Rainbow Wing on Rainbow Rock to make Ho-Oh appear, he was stopped by Cross and his Incineroar. Cross had been spying on the group for some time and had learned of their quest to find Ho-Oh. He wanted to battle Ho-Oh and tried to steal the Rainbow Wing from Ash. They engaged in another battle and this time Ash managed to beat Cross with his newly evolved Charizard. Despite this, Cross still took the Rainbow Wing however, and placed it atop Rainbow Rock. Due to Cross's evil heart, the Rainbow Wing became corrupted, which in turn corrupted the Marshadow from earlier and nearby wild Pokémon. With newfound power from the corrupted Rainbow Wing, the corrupted Marshadow was able to control the wild Pokémon and had it turn against the humans.
Ash and Pikachu tried to stop Marshadow, but Pikachu got heavily injured in the process. While shielding Pikachu from the corrupted Pokémon, Ash took the full blast. His body slowly disappeared and all but his consciousness vanished. As a result of this, the corrupted Rainbow Wing withered and freed Marshadow and the other Pokémon of its control. Pikachu then took hold of Ash's hat and cried over the loss of his Trainer and best friend. Ash's consciousness woke up in a spirit world where he was all alone. Faintly hearing Pikachu's voice, Ash ran towards the sound. Because of this, his body started to regenerate in the real world in a bundle of light, and Pikachu connected with the light to reunite with Ash, fully reviving him.
Soon after, a new Rainbow Wing appeared before Ash. Ash placed the Rainbow Wing atop Rainbow Rock and this time it recognized the Trainer's pure heart. A rainbow appeared, followed by Ho-Oh flying over Mt. Tensei. Ho-Oh and Ash had a battle, and afterwards went their separate ways. After healing at a Pokémon Center, Ash, Verity, and Sorrel said their goodbyes to Cross, who had changed his ways and promised to battle against Ash again someday. Sometime after, Ash also split ways with Verity and Sorrel, who both went to pursue their own goals. Ash continued his journey with Pikachu, vowing to once become a Pokémon Master.
This listing is of Ash's known Pokémon in the anime:
This listing is of the Badges Ash has obtained:
In the manga
In the movie adaptations
Ash appeared in the manga adaptation of the 20th movie, where his role is mostly the same as it was in the movie.