What was the Japan-only 1998 Nintendo 64 Pokémon game that came before Pokémon Stadium?

The Japan-only 1998 Nintendo 64 Pokémon game that came before Pokémon Stadium was Pocket Monsters Stadium.

Pocket Monsters Stadium was developed and published by Nintendo for the Nintendo 64. It introduced 3D Pokémon battles and focused on competitive play rather than reproducing the full role-playing adventure of the Game Boy games.

The game originally had a much larger design ambition, including plans to feature all of the Pokémon from the Game Boy titles. During development, the playable roster was reduced, and the Japanese release ultimately centered on a limited selection of 40 Pokémon. It was released in Japan before the better-known international Pokémon Stadium.

The naming history creates an unusual trap. The Western Pokémon Stadium was released in Japan in 1999 and was itself called Pokémon Stadium 2 in Japan, because it followed Pocket Monsters Stadium. The international version expanded the concept and supported all 151 Pokémon from Red, Blue, and Yellow through the Nintendo 64 Transfer Pak.