Who is the main playable Pokémon in Pokémon Yellow?

Pikachu is the main playable Pokémon companion in Pokémon Yellow. Unlike Pokémon Red and Blue, the game gives the player Pikachu at the beginning and has Pikachu follow the player outside its Poké Ball.

Pokémon Yellow was designed to reflect elements of the television anime. Pikachu refuses to evolve with a Thunder Stone, and the player can obtain Bulbasaur, Charmander, and Squirtle during the adventure rather than choosing one of them at the start.

The game was released in Japan in 1998 as Pocket Monsters Pikachu. It later launched internationally as Pokémon Yellow Version: Special Pikachu Edition. Its Pikachu-centered presentation helped connect the games more directly to the anime’s popularity.

Pikachu is therefore the defining partner of Yellow, but the player can still catch many other Pokémon. The answer refers to the special starting companion, not the only Pokémon available in the game.