From Bulbapedia, the community-driven Pokémon encyclopedia.
Art from the Game Freak website
The Pokémon Number One Grand Prix, known better as the P1 Grand Prix, is a special Pokémon battle tournament run by Silph Co. held especially for Fighting-type Pokémon in Celadon City. Each Pokémon Trainer who enters chooses only one Pokémon and engages in a series of one on one battles. The prize is a golden championship belt. It has only appeared in The Punchy Pokémon, although it is referenced in A Tyrogue Full of Trouble.
Poster in the Fighting Spirit Gym
Ash's Primeape and Brock's Geodude were both entered into the P1 Grand Prix, with Geodude being knocked out by Giant's Hitmonlee under Jessie's ownership, and Primeape winning the tournament and the belt.
The P1 Grand Prix's definition of "Fighting-type Pokémon" for the tournament seems to be based on one from the Pokémon Trading Card Game rather than the Pokémon games or Pokémon anime, as Ground- and Rock-type Pokémon can apparently be entered as well. In the TCG, Fighting, Ground, and Rock are all considered a single type. The TCG Fighting symbol appears on the poster advertising the tournament in the Fighting Spirit Gym.
- Contradicting Japanese sources, Pokémon.com states the tournament is held in the outskirts of Fuchsia City.
- Pokémon.com refers to the full name of the tournament as the number one Pokémon Grand Prix.