A player must collect eight Gym Badges in the original Pokémon Red and Blue games.
Each badge is earned by defeating a Gym Leader in a Pokémon battle. The badges prove that the player has overcome Kanto’s Gym challenge and eventually allow access to the Pokémon League at Indigo Plateau, where the player faces the Elite Four and the rival.
The eight Gyms are associated with Pewter City, Cerulean City, Vermilion City, Celadon City, Fuchsia City, Saffron City, Cinnabar Island, and Viridian City. Their leaders specialize in different Pokémon types, although the game’s progression does not always require visiting them in a simple city-by-city order.
The number eight became a familiar structure across many later main-series Pokémon games, though each region introduced its own leaders, challenges, or variations. The original Kanto badge system is therefore both a specific game objective and a lasting series tradition.