The Nintendo 64 hosted Pokémon Stadium, the first Pokémon Stadium title released in Western regions.
Nintendo released Pokémon Stadium in Japan in 1999, followed by releases in Australia, Europe, and North America in 2000. The game presented Pokémon battles in 3D, a major visual change from the sprite-based Game Boy role-playing games.
Players could connect Pokémon Red, Blue, and Yellow through the Nintendo 64 Transfer Pak. This allowed them to use Pokémon from those Game Boy games in Stadium’s battles and competitions. The game also included four Cups, Gym Leader Castle, and several minigames.
The Japanese release history is slightly confusing: an earlier Japan-only title called Pocket Monsters Stadium appeared in 1998, while the Western Pokémon Stadium was released as the successor and used all 151 original Pokémon. That distinction makes the console question more precise than simply asking when Stadium first appeared.