Ho-Oh was the first Pokémon seen by Ash in the Pokémon anime.
In the opening episode, Ash looks into the sky during his journey and sees a large, rainbow-colored bird Pokémon flying above him. The creature is Ho-Oh, although Ash does not know its identity at the time. This brief appearance creates a mystery because Ho-Oh was not part of the Pokédex data available in the original games.
The episode focuses mainly on Ash receiving Pikachu and escaping a flock of Spearow, so viewers sometimes remember Pikachu as the first Pokémon shown. Pikachu was Ash’s first partner, but Ho-Oh appears earlier in the episode as the mysterious Pokémon in the sky.
Ho-Oh later became closely associated with the Johto games, Pokémon Gold and Silver, where it appears on the cover of Pokémon Gold and plays an important legendary role. Its early anime appearance therefore foreshadowed material that would become central to the franchise’s second generation.